ZIRCONIUM 

AND    ITS 

COMPOUNDS 


BY 

FRANCIS  P.  VENABLE 


American  Chemical  Society 
Monograph  Series 


BOOK  DEPARTMENT 
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GENERAL  INTRODUCTION 

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3 


4  GENERAL  INTRODUCTION 

branches  of  science  outside  his  own  specialty.  In  spite  of  the  facilities 
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GENERAL  INTRODUCTION  5 

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PREFACE 

I  wish  to  express  my  obligations  in  the  preparation  of  this  book  to 
the  Index  to  the  Literature  of  Zirconium  by  A.  C.  Langmuir  and 
Charles  Baskerville,  and  especially  to  the  compendium  given  by  R. 
Jacoby  in  Gmelin-Kraut's  Handbuch  der  anorganischen  Chemie. 

I  have  not  sought  to  record  every  observation  or  detail  given  in  the 
literature,  many  of  which  are  faulty  or  erroneous,  but  only  such  as 
seemed  to  have  an  essential  bearing  on  the  subject.  My  purpose  has 
been  to  give  a  systematic,  clear,  and  sufficiently  full  account  of  the 
chemistry  of  zirconium  which  should  prove  useful  in  connection  with 
the  increasing  interest  attaching  to  this  element. 

This  book  is  affectionately  inscribed  to  my  daughter,  Louise  M. 
Venable,  and  to  my  son,  Charles  S.  Venable,  both  of  whom  have  ren- 
dered invaluable  aid  in  its  preparation. 


FRANCIS  P.  VENABLE 


University  of  North  Carolina 
June,  1921 


CONTENTS 


PAGE 

CHAPTER  I.    HISTORY  AND  OCCURRENCE 15 

CHAPTER  JI.    ZIRCONIUM  AND  ITS  PROPERTIES     ....      22 

Preparation. — Specific  Gravity. — Thermal. — Electrical.— 
Chemical. 

CHAPTER  III.    COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS      34 

With  Hydrogen. — With  Oxygen. — With  Hydrogen  and  Oxy- 
gen.— Higher  Oxides. — With  Nitrogen. — With  Carbon. — 
With  Sulphur.— With  Boron.— With  Silicon.— With  Phos- 
phorus. 

CHAPTER  IV.    COMPOUNDS  OF  ZIRCONIUM  WITH  THE  HALOGENS 

AND  THEIR  ACIDS 53 

With  Fluorine.— With  Chlorine.— With  Bromine.— With 
Iodine. 

CHAPTER  V.    COMPOUNDS  WITH  THE  ACIDS  OF    SULPHUR  AND 

SELENIUM 76 

With  Sulphurous  Acid. — With  Thiosulphuric  Acid. — With 
Sulphuric  Acid. — With  Selenious  Acid. — With  Selenic  Acid. 

CHAPTER  VI.    COMPOUNDS  WITH  ACIDS  OF  THE  NITROGEN  GROUP 

AND  RARE  INORGANIC  ACIDS 87 

With  Nitric  Acid. — With  Acids  of  Phosphorus. — With  Acids 
of  Arsenic. — With  Acids  of  Antimony. — With  Chromic  Acid. 
—With  Tungstic  Acid.— With  Molybdic  Acid.— With  Va- 
nadic  Acid. 

CHAPTER  VII.    COMPOUNDS  WITH  ACIDS  OF  THE  SILICON  GROUP      97 
With  Titanic  Acid.— With  the  Silicic  Acid. 

CHAPTER  VIII.    ZIRCONIC  ACID  AND  THE  ZIRCONATES    .       .       . 

Zirconic  Acid. — The  Zirconates. 

9 


10  CONTENTS 

PAGK 

CHAPTER  IX.    COMPOUNDS  WITH  ORGANIC  ACIDS  AND  RADICALS    110 

With  Carbonic  Acid. — With  Formic  Acid. — With  Acetic 
Acid.— With  Citric  Acid.— With  Oxalic  Acid.— With  Tar- 
taric  Acid. — With  Benzoic  Acid. — With  Salicylic  Acid. — 
With  the  Cyanogen  Acids. — Zirconium  Tetrahalides  with 
Organic  Bases  and  Radicals. 

CHAPTER  X.    ANALYTICAL  METHODS 120 

Qualitative. — Quantitative. — Separation  from  other  Ele- 
ments. 

CHAPTER  XI.    TECHNICAL  APPLICATIONS  OF  ZIRCONIUM  AND  ITS 

COMPOUNDS 126 

Precious  Stones. — Oxy-hydrogen  Light. — Gas  Mantles. — 
Incandescent  Filaments. — Alloys. — Furnace  Applications. — 
Refractories. — Enamels. — Glass. — Textile  Applications. — 
Colloidal  Applications. — Medicinal  Use. — Abrasive. — Chlo- 
rinating Agent. 

CHAPTER  XII.    PATENTS 133 

BIBLIOGRAPHY 149 

INDEX  171 


ZIRCONIUM 
AND  ITS  COMPOUNDS 

Chapter  I 
History 

While  this  element  is  widely  distributed,  and  fairly  abundant,  its 
similarity  in  general  properties  to  other  so-called  earths,  especially 
alumina,  the  difficulty  of  separation  from  them,  and  the  absence  of 
any  easy  characteristic  test  caused  it  to  escape  the  notice  of  the 
earlier  chemists.  It  is  a  mark  of  the  careful  analytical  work  done 
by  Klaproth  (392)  that  he  should  have  discovered  it  and  announced 
its  existence  conclusively  in  1789.  In  that  year  he  reported  that  in 
analyzing  the  jargon  of  Ceylon  he  had  obtained  31.5  p.c.  silica,  0.5  p.  c. 
iron  and  nickel  oxides,  and  68  p.c.  of  an  earth  differing  essentially 
from  all  known  to  him.  This  he  called  Zirkonerde.  A  few  years  later 
Klaproth  (393)  analyzed  also  the  hyacinth  of  France  and  found  the 
same  new  earth.  In  1797  Guyton  de  Morveau  (274)  published  his 
analyses  of  zircons  from  various  localities,  confirming  the  work  of 
Klaproth.  About  the  same  time  Vauquelin  (726)  examined  this 
new  earth,  to  which  the  name  zirconia  was  given,  and  detailed  the 
preparation  and  properties  of  some  of  its  compounds.  In  1798 
Trommsdorff  (711)  applied  all  of  the  methods  then  known  for  the 
decomposition  of  this  earth  but  without  success,  and  it  was  not  until 
1824  that  Berzelius  (50)  found  a  method  for  its  decomposition  and 
for  the  preparation  of  the  element  zirconium,  though  in  an  impure 
form.  Two  years  later  (53)  Berzelius  determined  its  atomic  weight. 

At  various  times  announcements  have  been  made  as  to  the  com- 
plexity of  zirconium  or  its  being  accompanied  by  some  hitherto  un- 
known element.  This  is  not  surprising  when  one  considers  the  large 
number  of  other  elements  which  have  been  recognized  as  present  in 
zircons,  the  prolonged  operations  necessary  for  complete  separations, 
and  the  ease  with  which  zirconium  forms  basic  compounds  of  varying 

15 


16  tl  ZIHQpNIUM  AND  ITS  COMPOUNDS 

dontent  and^widel/  differing  solubilities.  In  1845,  Svanberg  (692) 
claimed  that  in  decomposing  zircons  he  had  come  across  another  earth 
which  differed  from  zirconia  in  the  solubility  of  its  chloride,  of  the 
double  sulphate  with  potassium  and  of  its  oxalate,  and  which  also 
had  a  lower  atomic  weight.  This  earth  he  called  noria  and  the  sup- 
posed new  element  norium.  In  1853  Sjogren  (659)  believed  that  he 
had  found  this  noria  in  the  mineral  catapleiite.  According  to  his 
determinations  its  density  was  5.5  while  that  of  zirconia  was  4.3.  The 
existence  of  noria  was  satisfactorily  disproved  by  the  works  of  Ber- 
lin (43),  Hermann  (325),  Marignac  (468),  and  Knop  (400). 

In  1864  Nylander  (529)  reported  the  existence  of  two  earths  in 
zirconia,  an  observation  which  has  not  been  confirmed.  In  1869 
Sorby  (667)  announced  that  in  the  Ceylon  jargon  he  had  discovered 
a  new  element  with  a  peculiar  absorption  spectrum  to  which  he  gave 
the  name  jargonium,  but  later  (668,  669)'  found  he  had  fallen  into 
error  through  the  presence  of  a  small  amount  of  uranium,  which  is 
commonly  present  in  zircons  wherever  found.  In  the  same  year 
Church  (141)  drew  the  conclusion  from  his  spectroscopic  examination 
that  zirconium  was  accompanied  by  a  new  element  to  which  he  gave 
the  name  nigrium.  Here  again  is  an  illustration  of  the  ease  with 
which  a  mistake  can  occur  from  accompanying  impurities,  such  as 
thorium,  yttria,  and  the  rare  earths  which  are  found  in  the  zirconium 
minerals  coming  from  many  different  sources. 

The  announcement  by  Hofmann  and  Prandtl  (347)  that  about 
one-half  of  the  zirconia  obtained  from  euxenite  from  Brevig  con- 
sisted of  a  new  oxide  which  they  called  euxenerde  and  which  had  a 
considerably  higher  atomic  weight  has  not  been  confirmed  by  further 
investigation.  Hauser  and  Wirth  (301,  302)  working  with  twelve 
different  minerals  secured  from  widely  separated  localities  failed  to 
get  the  characteristic  reactions  reported  for  euxenerde.  Furthermore 
the  zirconia  was  separated  by  the  usual  methods  and  each  sample 
purified  by  fractionation  and  the  fractions  examined  spectroscopically 
with  the  result  that  there  was  no  decomposition  of  the  zirconium  nor 
separation  of  a  companion  element,  only  those  already  known  being 
identified. 

Occurrence 

While  zirconium  can  not  be  ranked  among  the  abundant  elements 
in  nature  it  is  widely  distributed  and  found  in  a  number  of  localities 
in  workable  quantities.  Since  no  delicate  and  characteristic  test  is 


HISTORY  17 

known  for  it,  its  presence  has  failed  of  detection  in  many  minerals. 
Traces  are  easily  lost  sight  of  when  it  accompanies  titanium,  alu- 
minum, and  the  rare  earths  in  small  amount. 

Zirconium  is  found  in  crystalline  rocks  (especially  in  granular 
limestone)  in  chloritic  and  other  schists,  in  gneiss,  syenite,  granite, 
and  beds  of  iron  ore.  The  syenitic  rock  called  "zircon  syenite"  con- 
tains crystals  of  zircon  along  with  epidote,  clseolite,  oligoclase,  and 
gegirine.  It  is  found  also  in  pegmatite,  sandstone,  ferruginous  sands, 
and  in  a  number  of  minerals  in  which  it  is  present  only  in  small 
amounts  or  traces.  So  constant  is  its  presence  in  the  older  igneous 
rock  that  Strutt  (688,  689)  has  made  use  of  its  uranium-lead  ratio 
as  a  means  of  calculating  their  relative  age.  Crystals  of  zircons  are 
common  in  auriferous  sands  and  are  found  in  volcanic  rocks. 

The  most  widely  distributed  and  abundant  mineral  containing 
zirconium  is  the  silicate,  known  in  the  common  form  as  zircon.  From 
this  the  name  of  the  element  is  derived.  It  has  a  hardness  of  7.5 
and  a  density  varying  from  about  4.0  to  4.7,  averaging  about  4.65. 
As  a  normal  silicate  its  theoretical  composition  would  be  ZrO2,  67.2 
p.c.;  Si02,  32.8.  The  percentage  of  zirconia  varies,  however,  from 
61  to  66.8  p.c.  The  most  common  impurity  is  iron,  but  quantitative 
analyses  (733)  show  traces  of  sodium,  potassium,  magnesium,  cal- 
cium, aluminum,  iron,  lead,  tin,  uranium,  erbium,  and  other  elements, 
and  Linnemann  (449)  found  in  addition  zinc,  copper,  bismuth,  man- 
ganese, cobalt,  and  nickel.  The  presence  of  some  of  these  is  doubtless 
due  to  infiltrations  in  the  cracks  of  the  crystals  from  the  surround- 
ing soil. 

There  are  references  to  zircons  in  very  early  times.  On  account 
of  its  hardness  it  was  used  as  a  material  from  which  to  cut  cameos 
and  engraved  signets.  Intaglii  of  zircons  are  not  at  all  uncommon 
among  ancient  gems.  Under  the  name  of  the  jacinth  it  is  mentioned 
by  Agricola  and  Interpe.  It  is  mentioned  also  in  the  Book  of  Revela- 
tion. The  jacinth  seems  to  have  been  the  colorless  or  yellowish 
variety.  Brownish,  orange,  or  reddish  varieties  were  known  as  hya- 
cinths and  sometimes  confused  with  topazes  and  garnets.  There 
would  seem  to  be  little  reason,  however,  for  the  substitution  for  jacinth 
in  the  revised  version  of  Revelation.  The  Ceylonese  called  it  jargon 
and  the  colorless  or  slightly  smoky  varieties  were  sold  as  inferior 
diamonds.  While  resembling  the  diamond  in  lustre,  they  were  less 
brilliant  and  not  so  hard  and  were  comparatively  worthless.  De  Lisle 
in  1783  writes  of  the  Diamant  Brut  or  Jargon  de  Ceylan.  One  singu- 


18  ZIRCONIUM  AND  ITS  COMPOUNDS 

lar  use  is  mentioned  by  Fourcroy,  who  says,  "The  hyacinth  from  Ex- 
pailly  (near  Le  Puy)  in  France  was  formerly  placed  in  collections  of 
the  materia  medica  to  be  used  in  some  pharmaceutic  compositions." 

The  zircons  of  Ceylon  are  mainly  found  in  alluvial  sands.  Those 
of  the  Ural  Mountains  are  chiefly  in  the  gold  regions.  They  are  also 
found  in  Greenland,  Norway,  Transylvania,  Bohemia,  the  Tyrol, 
France,  Italy,  Australia,  New  Zealand,  etc.  In  the  United  States  the 
zircon  is  commonly  associated  with  magnetite  sand  or  ore,  and  it  has 
been  found  in  a  number  of  states,  including  North  Carolina,  South 
Carolina,  Tennessee,  Oklahoma,  Florida,  New  York,  New  Jersey, 
Pennsylvania,  California,  Virginia,  and  others.  By  microscopic  ex- 
amination of  the  rocks  this  list  can  be  greatly  extended.  Its  com- 
mercial occurrence  is  chiefly  in  masses  of  pegmatite  and  pegmatized 
gneisses,  and  in  these  it  is  often  in  fairly  large  crystals,  weighing  up 
to  fifteen  pounds.  So  far  only  three  localities  in  the  United  States 
are  known  where  it  occurs  in  sufficient  quantities  for  mining.  These 
are  on  Green  River  in  Henderson  County,  North  Carolina,  at  Ander- 
son, South  Carolina,  and  near  Ashland,  Virginia.  Shipments  have 
been  made  from  the  first-named  locality  amounting  to  about  20,000 
pounds  since  1902  and  perhaps  60,000  pounds  prior  to  that  date. 
Very  large  crystals  weighing  as  much  as  fifteen  pounds  have  been 
found  at  Renfrew,  Canada,  but  the  supply  seems  to  be  limited. 
Opaque  green  zircons  have  been  found  in  St.  Lawrence  County,  New 
York,  and  black  ones  in  New  Jersey.  Small  but  very  beautiful  crys- 
tals, some  of  them  deep  emerald  green,  are  found  near  Pike's  Peak, 
Colorado.  In  the  volcanic  tufa  of  Vesuvius  it  is  found  in  small  white 
and  blue  octahedra. 

The  zircons  of  Ceylon  occur  mainly  in  alluvial  sands.  The  amount 
in  the  gold  regions  of  the  Ural  Mountains  is  said  to  be  large.  There 
appear  to  be  considerable  deposits  in  Greenland  and  Norway  and  also 
in  New  South  Wales. 

Microscopic  crystals  are  widely  distributed  in  the  sedimentary 
rocks,  the  material  having  been  largely  derived  from  the  older  rocks, 
e.g.,  in  the  variegated  sandstones  of  the  Black  Forest,  in  carboniferous 
limestones,  and  in  the  sands  of  the  valley  of  the  Main.  Thiirach  has 
shown  that  microscopic  zircon  is  rarely  absent  from  archsean  and 
sedimentary  rocks.  It  also  occurs  in  many  igneous  rocks  and  is 
widely  distributed  in  basalts  and  dolerites.  Its  resistance  to  weath- 
ering and  attrition  causes  the  zircon  to  be  found  in  many  auriferous, 
volcanic,  and  shore  sands.  The  researches  of  the  United  States  Geo- 


HISTORY  19 

logical  Survey  upon  the  black  sands  would  tend  to  show  its  universal 
presence  in  granite  and  allied  rocks. 

In  color  the  crystals  vary  from  colorless  through  a  number  of  colors 
as  amber,  smoky,  red,  reddish-brown,  blue,  green,  black  to  a  dull 
opaque  brown.  The  small  white  and  blue  octahedra  of  Vesuvius 
have  been  mentioned.  The  finest  gem  stones  come  from  Ceylon, 
Mudger,  and  New  South  Wales. 

Meyer  (485)  has  given  the  following  description  of  the  occurrence 
and  mining  of  the  native  zirconia  ore  in  Brazil.  The  deposits  are  in 
the  Caldas  region  which  lies  partly  in  the  State  of  Minas  Geraes  and 
partly  in  the  State  of  Sao  Paulo,  approximately  130  miles  north  of 
the  city  of  Sao  Paulo.  It  is  a  mountainous  plateau,  the  main  eleva- 
tion of  which  is  about  3600  feet.  The  surface  is  undulating,  present- 
ing differences  in  level  of  from  300  to  600  feet.  The  whole  area  is 
bounded  on  all  sides  by  ridges  rising  abruptly  from  600  to  1200  feet 
above  the  general  level  and  forming  a  roughly  elliptical  inclosure 
with  a  major  axis  of  approximately  20  miles  in  length  and  a  minor 
axis  of  15  miles.  The  predominant  rock  of  the  plateau  is  phonolite. 

The  ore  can  be  divided  roughly  into  two  classes.  First,  alluvial 
pebbles  ranging  in  size  from  one-half  inch  to  three  inches  in  diameter, 
generally  carrying  about  90-93  p.c.  of  zirconia.  The  pebbles,  known 
as  "favas"  and  having  a  density  of  4.8-5.2,  are  found  along  small 
stream  beds  and  on  the  talus  slopes  of  low  ridges.  Second,  zirconia 
ore  proper  or  zirkite,  which  ranges  in  shade  from  a  light  gray  to  a 
blue-black,  the  lighter  colored  material  carrying  a  larger  percentage 
of  zirconium  silicates  and  showing  a  minimum  content  of  73  p.c.  zir- 
conia. The  blue-black  ore  generally  carries  80-85  p.c.  of  zirconia. 

Prior  to  the  investigations  of  Derby  and  Lee  (177)  this  zirkelite 
was  considered  identical  with  baddeleyite.  It  has  now  been  shown 
that  it  is  a  mechanical  mixture  of  three  minerals,  namely,  brazilite, 
zircon,  and  a  new  and  unnamed  zirconium  silicate  carrying  about  75 
p.c.  of  zirconia.  This  new  mineral  has  the  same  crystal  form  as  zircon 
but  is  readily  soluble  in  hydrofluoric  acid,  while  zircon  is  practically 
not  attacked. 

Several  large  outcrops  of  the  ore  occur  on  the  extreme  westerly 
edge  of  the  plateau,  one  or  two  boulders  weighing  as  much  as  30  tons. 
Owing  to  the  hardness  of  the  ore  it  is  almost  impossible  to  drill  holes 
for  explosives,  and  in  handling  large  masses  it  is  found  necessary  to 
resort  to  the  primitive  method  of  heating  the  rock  and  suddenly  cool- 
ing with  water.  In  some  of  the  deposits  the  ore  occurs  in  the  form 


20  ZIRCONIUM  AND  ITS  COMPOUNDS 

of  gravel  and  large  pebbles  embedded  in  a  reddish  clay.  On  drying 
the  ore  can  be  separated  by  screening.  It  is  washed  thoroughly  clean 
from  ferruginous  matter  before  shipping.  Transportation  of  the  ore 
to  the  nearest  railroad  is  difficult.  From  surface  indications  the  de- 
posits are  of  vast  extent.  The  shipment  of  this  ore  reached  in  1913 
a  total  of  1,119  tons.  The  maximum  production  of  ore  in  the  United 
States  (practically  all  from  North  Carolina)  was  reached  in  1905 
with  a  yield  of  4  tons. 

It  is  evident  that  the  most  important  commercial  source  of  zir- 
conium is  the  native  zirconia  of  Brazil  whose  occurrence  has  been 
described.  This  Brazilian  ore  is  reasonably  pure  and  may  be  used 
direct  in  refractories  as  zirconia  or  can  be  easily  converted  into  the 
desired  compounds,  which  is  much  more  difficult  in  the  case  of  zir- 
cons. Baddeleyite  is  the  mineralogical  name,  and  distinct  fibrous 
bbtyroidal,  or  columnar  crystals  of  this  mineral  are  found  in  the  ore, 
which  is  known  as  brazilite.  Jacupirangite  is  a  variety  of  baddeley- 
ite also  crystalline.  Besides  the  occurrence  of  baddeleyite  in  Brazil 
it  has  been  found  in  the  United  States,  Ceylon,  Sweden,  and  Italy. 
The  commercial  ore  is  often  called  zirkite  and  has  some  zircon  mixed 
with  it.  Zirkelite  is  also  present  and  is  a  variety  of  zirconium  silicate 
containing  about  50  p.c.  of  zirconia. 

Zirconium  has  been  reported  (317,  478)  as  present  in  certain 
spring  waters  and  its  presence  has  been  detected  (615)  in  the  solar 
spectrum.  It  has  also  been  reported  as  having  been  found  in  a 
meteorite,  but  the  identification  seems  to  have  been  incomplete. 

LIST  OF  ZIRCONIUM   MINERALS. 

Adelfolith  or  p.c.ZrO2 

malacone  weathered  zircon  47.42 

Alvite  weathered  zircon  39-3248 

Anderbergite  R3  V2Zr9(SiO2)12.18  H2O  '   41.2 

Arrhenite  hydrated  silicotitanate  of  Zr,  Fe,  Ce,  Er  342 

Astrophyllite  (SiTiZr)5Olfl(MnFe)4(KNaH)4  4.97 

Auerbachite  weathered  zircon  55.18 

Baddeleyite  native  zirconia  up  to  99^0 

Beccarite  zircon  containing  Ca  and  Fe  62.16 

Brazilite  see  baddeleyite  800 

Catapleiite  H2(Na2Ca)ZrSi3Ou  30.-40' 

Chalkolamprite  a  niobate-silicate  of  Zr  '    57 

Cyrtolite  weathered  zircon  36-61 

Elpidite  Na2Si205.Zr(Si205)2  '  20^ 

Erdmannite  basic  silicate  of  cerium  earths  and  ZrO2                      varying 

Eudialyte  Na13(CaFe)6(SiZr)2oOS2Cl  10-20 

Fergusomte  niobate  (tantalate)  Yt,  Ce,  U,  Th,  etc,  up  to  7. 

Hiortdahhte  zircon  pyroxene  21 5 

Kochelite  niobate  of  yttria  earths 


HISTORY  21 

LIST  OF  ZIRCONIUM  MINERALS. 


p.c. 

Lovenite  (SiO3)2  MnCaFe.(ZrOF)Na  30. 

Mosandrite  Zr,  Th,  Ce,  Ti  silicate  7.4 

Oliveiraite  3ZrO2.2TiO2.2H2O  63.36 

Orvillite  8ZrO2  .  6SiO2  .  5H2O  71.88 

Polymignite  metazirconotitanate  and  tantaloniobate  14.-30. 

Pyrchlor  niobate-titanate 

Rosenbuschite  zircon  pyroxene  20. 

Tachyaphaltite  weathered  zircon  39. 

Tantalite  a  tantalate  (niobate)  up  to  11. 

Uhligite  (ZrTi)O5.Ca.(TiAl)O5Al  22. 

Wohlerite  SiMZr3Naa04SF,  .  Ca10Na5  15.-23. 

Zirkelite  zirconium  silicate  50. 

In  the  following  minerals  zirconium  is  found  in  small  amounts: 
Auerodite,  bragite,  cerite,  columbite,  edwardsite,  eucrasite,  hypers- 
thenite,  johnstrupite,  leukosphenite,  karyocerite,  knopite,  koppite, 
mackintoshite,  melanocerite,  monazite,  niobate,  nohlite,  samarskite, 
seybertite,  sillimanite,  sipylite,  tritonite,  tschefifkinite,  tyrite,  uhligite, 
uraninite,  vietinghoflSte,  xeontime,  yttergranate,  and  zoisite. 

The  zirconium  minerals  have  been  classified  under  the  following 
types: 

1.  Zircon  type.    Adelfolith,  alvite,  anderbergite,  arrhenite,  auer- 
bachite,    benarite,    engelhardite,    erdmannite,    hiortdahlite,    ilmenite, 
malacone,   mosandrite,   oerstedtite,   ostranite,   pyrobuschite,   tachya- 
phaltite,  zircon. 

2.  Add  type.      Astrophyllite—  (SiTiZr)5016(MnFe)4(KNaH4)— 
and  elpidite  —  Si4Zr010.Na2  —  eudialite,  fergusonite,  catapleiite,  leuko- 
sphenite, lovenite,  polymignite,  wohlerite. 

3.  Oxide  type.    Baddeleyite,  brazilite,  zirkelite. 

4.  Tantalate  type.    Bragite,  chalkolamprite,  pyrochlor,  tantalite. 


Chapter  II 

Zirconium  and  its  Properties 
Preparation  .of  Zirconium 

The  preparation  of  metallic  zirconium  presents  many  difficulties 
and  numerous  .attempts  during  nearly  a  century  failed  to  produce  the 
metal  reasonably  free  from  impurities.  Some  of  the  chief  obstacles 
arise  from  its  strong  affinity  for  oxygen,  and  hence  the  difficulty  of 
reducing  the  oxide  and  the  ease  with  which  the  metal  is  reoxidized 
at  high  temperatures;  also  the  readiness  with  which  it  absorbs  and 
combines  with  hydrogen,  nitrogen,  boron,  and  silicon,  and  its  tendency 
to  form  alloys  with  the  light  metals  such  as  aluminum  and  mag- 
nesium. 

It  was  along  the  line  of  the  reduction  of  the  oxide  that  the  first 
efforts  to  produce  the  metal  were  made  and  failed.  These  were  by 
Trommsdorff  (711)  in  1798  and  Davy  (170)  in  1808.  Attempts  at 
reducing  zirconia  in  a  stream  of  hydrogen  failed  and  it  is  now  known 
that  even  had  they  succeeded  the  hydride  would  have  been  formed 
if  the  temperature  had  not  exceeded  800°.  Nor  can  the  tetrachloride 
be  reduced  by  hydrogen  at  a  temperature  under  600°. 

In  1824  Berzelius  (50)  first  prepared  the  metal  by  the  reduction 
of  the  double  fluoride  of  zirconium  and  potassium  by  means  of  potas- 
sium. 

2KF .  ZrF4  +  K±  =  6KF  +  Zr. 

The  dried  and  finely  powdered  double  fluoride  was  heated  in  layers 
of  potassium  in  a  small  iron  cylinder  closed  at  one  end,  and  placed 
in  a  platinum  crucible,  covered  with  a  top.  This  mixture  was  stirred 
with  an  iron  wire  and  heated  over  a  lamp,  first  gently  and  then  to 
low  red  heat.  In  this  way  the  reduction  went  on  quietly.  On  treat- 
ing the  cooled  mass  with  water  a  little  hydrogen  was  evolved  and 
amorphous  zirconium  separated.  This  contained  some  zirconia.  It 
was  further  washed  with  water,  digested  for  six  hours  at  40°-50° 
with  equal  parts  of  hydrochloric  acid  and  water,  then  washed  on  a 

22 


ZIRCONIUM  AND  ITS  PROPERTIES  23 

filter  with  a  solution  of  ammonium  chloride,  and  lastly  with  alcohol. 
The  product  was  impure  and  observations  made  upon  it  as  to  the 
characteristics  of  elementary  zirconium  were  consequently  inaccurate. 
Subsequent  experiments  seem  to  show  that  the  double  fluoride  is  the 
best  source-material  for  the  preparation  of  the  metal,  a  tribute  to 
the  knowledge  and  skill  of  Berzelius,  but  many  modifications  in  the 
method  as  outlined  above  have  been  gradually  introduced.  Franz 
(230)  found  the  double  fluoride  3KF.ZrF4,  prepared  as  minute  crys- 
tals by  precipitation  with  an  excess  of  potassium  fluoride,  to  be  pref- 
erable to  2KF.ZrF4  but  used  aluminum  as  a  reducing  agent,  heating 
the  mixture  in  a  graphite  crucible.  He  obtained  an  alloy  of  zir- 
conium, however,  containing  1.03  p.c.  of  aluminum  and  0.17  p.c.  of 
silicon.  The  temperature  was  kept  high  to  lower  the  contents  of 
aluminum.  Troost  (713,  714)  repeating  the  experiment  of  Berzelius, 
obtained  the  same  amorphous  zirconium  mixed  with  zirconia.  His 
reduction  by  means  of  aluminum  yielded  crystals  in  the  form  of 
oblique  prisms  which  were  separated  by  means  of  dilute  hydrochloric 
acid  and  revealed  on  analysis  the  presence  of  both  aluminum  and 
silicon.  They  showed  an  easy  cleavage  and  had  a  density  of  4.15, 
were  more  fusible  than  silicon,  and  resisted  the  action  of  oxygen  at 
red  heat.  At  white  heat  a  coating  of  oxide  was  formed.  They  com- 
bined with  chlorine  with  incandescence  and,  at  fusion  temperatures, 
decomposed  caustic  alkalies  with  the  evolution  of  hydrogen.  They 
were  slightly  soluble  in  hot  sulphuric  acid  and  easily  dissolved  by 
aqua  regia  and  hydrofluoric  acid. 

Wedekind  (776)  attempted  the  reduction  of  the  double  fluoride 
with  aluminum,  obtaining  different  products  according  to  the  method 
of  procedure,  which  on  analysis  indicated  various  alloys  with  alu- 
minum, namely,  ZrAl2,  Zr3Al4,  ZrAl3. 

He  also  (785)  repeated  the  method  of  Berzelius  with  precautions 
to  prevent  oxidation.  Sodium  was  found  to  be  preferable  to  potas- 
sium as  the  reducing  agent.  The  product  was  dried  at  200°  in  vacuo, 
leaving  a  hygroscopic  preparation.  This  was  further  heated  to  300° 
in  vacuo,  becoming  then  pyrophoric,  catching  on  fire  on  exposure  to 
air  fourteen  hours  after  cooling.  The  product  obtained  by  Berzelius, 
he  concluded,  was  a  mixture  of  very  finely  divided  metal  and  zirconia. 
Some  investigators  had  suggested  that  the  oxide  formed  was  a  sub- 
oxide.  Wedekind's  conclusions,  however,  were  against  this.  The  ex- 
istence of  this  oxide,  ZrO,  has  been  maintained  by  Winkler  (817)  and 
Dennis  and  Spencer  (176).  The  metal  in  very  fine  subdivision  seems 


24  ZIRCONIUM  AND  ITS  COMPOUNDS 

to  be  very  susceptible  to  the  action  of  oxygen,  nitrogen,  etc.,  probably 
on  account  of  the  large  surface  exposed. 

A  zirconium  said  to  be  of  great  purity  was  prepared  by  Weiss  and 
Naumann  (806).  They  made  use  of  the  Berzelian  method,  substitut- 
ing sodium  for  potassium  and  further  purifying  the  product.  Also 
commercial  zirconium  was  bought  from  dealers  and  purified  as  fol- 
lows: The  impure  metal  was  pressed  into  pencils  and  used  as  the 
electrodes  in  a  bomb  which  had  been  exhausted  of  air,  then  filled 
with  hydrogen  and  this  also  pumped  out.  After  several  repetitions 
the  hydrogen  was  reduced  to  a  pressure  of  10-11  mm.  and  the  electric 
current  turned  on.  The  zirconium  pencils  were  kept  at  a  distance  of 
2-3  mm.  The  current  used  was  one  of  60-70  amperes  at  20-25  volts. 
The  metal  of  the  positive  electrode  melted  and  fell  in  drops  upon  the 
negative  electrode  which  was  placed  underneath.  The  metal  collected 
in  various  experiments  was  found  to  range  from  99.76  p.c.  to  99.89  p.c. 
pure.  When  ammonia  under  diminished  pressure  was  substituted  for 
hydrogen,  metal  ranging  from  99.69  p.c.  to  99.81  p.c.  pure  was  ob- 
tained, showing  that  at  this  temperature  zirconium  apparently  does 
not  react  with  either  hydrogen  or  nitrogen. 

Attempts  to  reduce  zirconia  by  means  of  magnesium  were  made 
by  Phipson  (547)  and  by  Bailey  (19).  The  resulting  product  re- 
tained oxide.  Also  Wedekind  (776)  prepared  amorphous  zirconium 
by  heating  thin  pencils  of  the  double  fluoride  with  magnesium  in  an 
electric  furnace  with  a  current  of  90-100  amperes.  This  gave  a  dark, 
somewhat  metallic-like  mass  containing  94.12  p.c.  of  zirconium.  A 
later  experiment  (787)  yielded  a  compact  metal  with  96.55  p.c.  zir- 
conium and  4.14  p.c.  oxygen.  Warren  (761)  states  that  zirconium  can 
be  reduced  from  solutions  of  its  salts  by  the  replacement  action  of 
magnesium.  Wedekind  (777)  heating  zirconia  in  a  nickel  crucible 
with  40  p.c.  over  the  theoretical  quantity  of  magnesium  obtained  a 
colloidal  zirconium  (purity  not  determined)  which  was  deep  blue 
in  reflected  light.  On  the  passage  of  an  electric  current  the  particles 
migrated  with  the  positive  stream,  which  is  opposite  to  the  observa- 
tion of  Whitney  (814). 

Tucker  and  Moody  (723),  who  tried  the  reduction  of  zirconia  by 
the  Goldschmidt  method,  were  unsuccessful.  Attempts  by  Wede- 
kind (773)  to  reduce  zirconia  by  means  of  boron  yielded  the  boride. 
When  carbon  was  used  the  carbide  was  formed.  Moissan  (500)  in 
an  electric  furnace  with  a  current  of  360  amperes  and  70  volts 
brought  powdered  zircons  to  fusion  and  boiling  with  the  giving  off 


ZIRCONIUM  AND  ITS  PROPERTIES  25 

of  white  fumes.  He  states  that  in  a  carbon  crucible  he  obtained 
metal  containing  neither  carbon  nor  nitrogen.  On  mixing  the  zircons 
with  an  excess  of  carbon  a  carbide  was  formed  having  4.22-5.10  p.c. 
of  carbon.  This  product  gradually  decomposed  in  the  air.  By  fusing 
together  the  zirconium  carbide  and  zirconium  thus  prepared  he  ob- 
tained metallic  zirconium.  The  metal  was  very  hard,  scratching 
glass  and  rubies  and  having  a  density  of  4.25.  The  pure  metal,  how- 
ever, shows  a  wide  variation  from  these  properties,  so  Moissan  was 
probably  in  error  as  to  the  purity  of  his  preparatoin. 

Wedekind  (785)  found  it  possible  to  reduce  zirconia  by  means  of 
calcium: 

Zr02  +  Ca2  =  Zr  +  2CaO. 

Commercial  calcium  was  used  (91.8-94.9  p.c.  Ca.).  The  impurities 
were  iron,  silicon,  and  chlorine.  The  mixture  was  placed  in  an  iron 
tube  which  was  then  exhausted  to  0.5-0.1  mm.  pressure.  This  was 
heated  until  the  reaction  set  in  and  then  the  reaction  moderated  by 
cooling.  The  porous,  baked  mass  was  withdrawn,  wrashed  with  water, 
alcohol,  dilute  hydrochloric  acid,  and  finally  acetone,  dried,  and 
heated  in  vacuo.  On  polishing  it  gave  a  fine  metallic  mirror.  Anal- 
ysis showed  97.7  p.c.  zirconium,  the  remainder  being  zirconia.  It  was 
samples  of  this  preparation  which  were  sent  to  Burgess  and  v.  Bolt  on 
for  the  determination  of  the  melting  point.  The  density  was  found 
to  be  6.2.  Sander  (633)  has  patented  a  method  for  preparing  zir- 
conium by  heating  in  vacuo  the  hydride  or  nitride  under  the  con- 
tinuous withdrawal  of  the  gases  formed. 

Lely  and  Hamburger  (440)  have  prepared  a  very  pure  zirconium 
by  heating  zirconium  tetrachloride  and  sodium  in  a  bomb  with  an 
electric  current.  The  metal  was  obtained  in  lamina?  which  could  be 
pressed  into  rods.  It  was  very  ductile  and  gave  a  mirrorlike  surface 
on  burnishing.  It  was  easily  oxidized  on  heating,  dissolved  in  cold 
hydrofluoric  acid,  concentrated  or  dilute,  and  in  concentrated  hot 
sulphuric  acid,  also  in  hot  aqua  regia.  The  analysis  given,  namely, 
0.2154  grams  of  metal  yielding  0.2915  grams  of  zirconia,  would  prove 
it  to  be  exactly  100  p.c.  pure  if  the  atomic  weight  is  taken  as  90.6. 

Becquerel  (35)  was  the  first  to  attempt  the  preparation  of  the 
metal  by  electrolysis.  Very  concentrated  solutions  of  the  chloride 
were  subjected  to  the  action  of  the  voltaic  pile.  The  metal  was  gotten 
in  the  form  of  a  black,  amorphous  powder  which  was  acted  upon  by 
air.  Troost  (714)  by  the  electrolysis  of  the  melted  double  fluoride 


26  ZIRCONIUM  AND  ITS  COMPOUNDS 

obtained  lustrous  crystalline  laminae  which  decomposed  cold  water. 
Wedekind  (774)  on  repeating  this  experiment  obtained  only  impure, 
amorphous  zirconium  as  a  gray-black,  easily  oxidized  powder. 

Colloidal  zirconium.  Several  of  the  methods  for  preparing  zir- 
conium yield  part  of  it  in  such  finely  divided  form  that  it  is  appar- 
ently in  the  colloidal  form.  Thus  Wedekind  (774,  780,  782)  reported 
that  when  the  double  potassium  and  zirconium  fluoride  is  reduced  by 
potassium,  the  excess  of  potassium  removed  by  alcohol  and  the  potas- 
sium fluoride  by  washing  with  water  and  a  solution  of  potassium 
nitrate,  part  of  the  zirconium  in  the  final  washing  with  water  passes 
through  the  filter.  When  this  is  subjected  to  dialysis  the  hydrosol 
in  transmitted  light  is  gray-black  in  color  and  in  reflected  light  an 
opalescent  black.  It  shows  a  relatively  high  stability  to  acid  elec- 
trolytes while  alkaline  electrolytes  coagulate  it.  The  hydrogel  sepa- 
rates in  black  flocks.  Neutral  electrolytes  cause  no  direct  coagula- 
tion. A  white  precipitate  which  is  redissolved  on  shaking  may  be 
formed.  Hydrochloric  acid  precipitates  it  on  prolonged  boiling.  Hy- 
drogen dioxide  causes  immediate  precipitation. 

Again  (777,  814),  when  zirconia  is  reduced  by  an  excess  of  mag- 
nesium ground  with  water,  treated  with  warm,  concentrated  ammo- 
nium chloride  solution  and  then  warm,  dilute  hydrochloric'  acid  part  of 
the  solid  goes  through  a  filter,  giving  a  colloidal  solution  which  is  deep 
blue  in  transmitted  light.  The  particles  migrate  with  the  positive 
stream  towards  the  cathode.  This  latter  observation  is  opposed  to 
that  of  Whitney  (814),  who  found  the  supposed  colloidal  zirconium 
under  the  influence  of  the  electric  potential  to  migrate  in  the  direction 
of  the  negative  stream.  This  colloidal  matter  may  have  been  con- 
taminated with  the  nitride,  hydride,  or  with  some  partially  oxidized 
metal.  A  colloidal  solution  of  a  similar  blue-black  color  has  been 
prepared  from  unreduced  zirconia. 

Properties  of  Zirconium 

So  far  as  zirconium  has  been  prepared  in  a  condition  of  reason- 
able purity  it  seems  to  be  known  only  as  an  amorphous  black  powder, 
which  when  melted  is  steel-gray  and  on  burnishing  gives  a  lustrous 
metallic  mirror.  The  existence  of  a  crystalline  and  a  graphitic  form 
has  at  least  not  been  established.  Investigators  who  have  reported 
them  had  alloys  rather  than  the  pure  metal  in  hand.  It  is  natural 
that  in  earlier  times  their  existence  should  have  been  surmised  from 


ZIRCONIUM  AND  ITS  PROPERTIES  27 

the  analogy  of  its  congener,  carbon.  The  element  has  been  prepared 
in  a  colloidal  form,  though  some  doubt  exists  as  to  its  elementary 
condition  in  this  form.  Its  degree  of  hardness  has  not  been  satis- 
factorily determined.  The  data  of  Moissan,  namely,  4.7,  and  power 
to  scratch  rubies  are  evidently  to  be  referred  to  the  carbide  or  mix- 
ture of  metal  and  carbide.  Marden  and  Rich  (467)  gave  the  hard- 
ness as  6.7. 

Specific  Gravity.  Many  of  the  determinations  of  the  density  are 
quite  unreliable  on  account  of  impurities  in  the  samples  taken.  Such, 
for  instance,  are  the  figures  given  by  Troost  (713),  4.15;  by  Meyer 
(489),  4.08;  by  Moissan  (500),  4.25.  Wedekind  (785)  out  of  a  series 
of  determinations  on  metal  over  99.5  p.c.  pure  preferred  the  figures 
6.29.  Weiss  and  Naumann  (806),  using  also  very  pure  metal  (99.8 
p.c.),  reported  the  density  as  6.4.  The  close  accord  of  the  two  last 
observers  would  lead  to  the  conclusion  that  6.4  is  to  be  taken  as  the 
density  of  the  pure  metal.  The  atomic  volume  then  is  14.16  (At.wt. 
90.6). 

Melting  Point.  The  discrepancies  in  the  few  determinations  which 
have  been  made  of  this  constant  are  serious  and  now  that  the  metal 
can  be  prepared  in  purity  a  careful  redetermination  is  demanded. 
Supposedly  pure  metal  was  furnished  by  Wedekind  to  both  v.  Bolton 
and  Burgess.  The  former  (89) ,  using  a  vacuum  furnace  and  Siemens 
and  Halske  optical  pyrometers,  which  had  a  probable  error  of  50° 
at  the  temperature  used,  gave  as  the  results  of  two  experiments  2330° 
and  2380°  or  an  approximate  mean  of  2350°.  This  is  near  the  melt- 
ing point  of  zirconia.  Burgess  (113)  used  a  platinum  support  so  that 
the  possible  formation  of  an  alloy  was  not  eliminated.  Still  the 
method  was  tested  with  iron,  chromium,  cobalt,  nickel,  and  man- 
ganese, where  the  same  possible  source  of  error  existed,  and  results 
were  obtained  in  accord  with  the  known  melting  points  of  these  metals. 
His  three  experiments  with  zirconium  gave  1529°,  1533°,  1523°,  and 
he  adopted  the  figure  1530°  for  the  melting  point.  Marden  and  Rich 
(467)  gave  the  melting  point  as  a  little  over  1600°.  Guertlar  and 
Pirani  (270)  give  a  probable  melting  point  of  1700°. 

Specific  Heat.  The  earliest  determination  of  the  specific  heat 
was  made  by  Mixter  and  Dana  (499).  The  figure  obtained  was 
0.0667  at  99.7°.  This  would  give  an  atomic  heat  of  6.07.  The  speci- 
men of  zirconium  contained  silicon  and  probably  other  impurities. 
Wedekind  and  Lewis  (786)  found  the  specific  heat  to  be  0.06725, 
which  would  give  an  atomic  heat  of  6.1.  Later  determinations  by 


28  ZIRCONIUM  AND  ITS  COMPOUNDS 

Wedekind  (785)  gave  the  range  for  different  samples  as  0.0656  to 
0.0735,  or  an  atomic  heat  of  6.19  to  6.66.  Weiss  and  Naumann  (806) 
with  a  very  pure  specimen  obtained  the  high  result  of  0.0804,  or  an 
atomic  heat  of  7.31.  The  latter,  if  confirmed,  would  assign  to  zir- 
conium the  highest  atomic  heat  known.  All  these  determinations 
were  apparently  made  at  the  range  0°-100°.  Dewar  (186)  has  deter- 
mined the  specific  heat  at  temperatures  between  that  of  liquid  nitro- 
gen and  liquid  hydrogen,  finding  it  to  be  0.0262,  which  gives  an  atomic 
heat  of  2.38  at  that  range. 

Electrical  Properties.  Meyer  (489),  making  use  of  commercial 
specimens,  found  zirconium  to  be  diamagnetic  and  with  an  atomic 
magnetism  k  =  0.0114  X  10'6  at  17°.  Pure  amorphous  zirconium  is 
a  conductor  of  electricity.  When  pressed  into  pencils  it  can  be  used 
as  electrodes  for  the  arc.  For  filaments,  rhodium  has  sometimes  been 
added.  Bohm  (83)  has  recorded  a  number  of  observations  as  to  the 
conductivity  of  zirconium  filaments.  Owen  (533)  has  examined  the 
thermomagnetic  properties  of  zirconium,  determining  the  specific  sus- 
ceptibility which  is  equal  to  the  field  intensity  divided  by  the  density. 
The  determinations  were  made  on  "crystallized  zirconium." 

Optical  Properties.  Karl  (382)  has  reported  his  experiments  upon 
the  triboluminescence  of  zirconium  in  compounds.  Gladstone  (245) 
found  the  specific  refraction  of  zirconium  to  be  0.242  and  the  atomic 
refraction  21.9. 

Spectrum.  The  earliest  examination  of  the  spark  spectrum  of 
zirconium  was  made  in  1869  by  Thalen  (701).  This  was  in  the  visible 
spectrum  and  twenty-six  lines  are  recorded  with  their  intensity  on  the 
old  scale.  They  are  as  follows: 

I  i  I  i 

Orange           6343.5  3  Indigo  4497.5  4 

6310.0  3  "  4494.5  4 

6140.5  1  "  4443.0  4 

6132.5  3  "  4380.0  4 

6127.0  1  "  4370.0  4 

Yellow           5384.5  4  "  4360.0  4 

5349.5  3  "  4242.0  4 

Green             5190.5  3  "  4241.5  4 

4815.0  1  Violet  4228.5  4 

4771.0  1  "  4209.5  4 

4738.5  1  "  4209.0  4 

4709.5  1  "  4155.0  2 

4686.5  1  4149.0  2 

The  spectrum  of  zirconium  is  especially  rich  in  ultra-violet  lines. 
Exner  and  Haschek  (214)  have  measured  1424  of  these  lines.  The 


ZIRCONIUM  AND  ITS  PROPERTIES  29 

zirconium  used  was  prepared  by  the  Moissan  method  and  hence  prob- 
ably contained  carbon  and  other  impurities.  The  chief  lines  and 
their  intensity  (Rowland's  scale)  are  given  by  Gmelin  and  Kraut.1 

I  i                                 I  i 

3392.20  20  3958.39  20 

3438.39  20  3991.31  20 

3496.40  20  3999.18  20 
3556.89  20  4149.43  20 

3698.41  20  4209.21  20 
3751.85  20  4380.12  20 
3836.98  20 

The  arc  spectrum,  according  to  Rowland  and  Harrison  (616) ,  gives 
820  lines,  of  which  the  chief  are  the  following: 

I  i  I  i 

3392.14  10  4227.94  10 

3496.38  10  4239.49  10 

3890.49  10  4282.36  10 

3891.53  10  4507.32  10 

3929.71  10  4535.90  10 

3973.63  10  4575.69  10 

4081.40  10  4688.00  10 

Vehle  (731)  has  measured  the  arc  spectrum  in  terms  of  the  interna- 
tional normal.  As  a  means  of  spectroscopic  detection  de  Gramont 

(253)  has  recommended  the  use  of  the  five  lines  in  the  blue  between 
481.6  and  469,  especially  474.0. 

The  measurement  of  the  ultimate  rays  of  greatest  photographic 
sensibility  (international  normal)  has  also  been  given  by  de  Gramont 

(254)  as  follows: 

Rays  1/100  1/1000         5/10000        1/10000        5/100,000 

3698.16  +  ? 

3572.47  +  ? 

3505.66  -|-  + 

3496.20  4-  +  -f- 

3438.23 

3391.98  +  4- 

3273.04  +  4- 

The  decomposition  of  the  zirconium  lines  into  their  components 
has  been  investigated  by  Moore  (503) .  The  visible  arc  spectrum  has 
also  been  mapped  by  Eder  and  Valenta  (206) .  They  found  it  easiest 
to  obtain  by  using  the  halides,  as  the  oxy-compound  gave  a  continuous 
spectrum  from  the  glowing  oxide.  In  the  oxy-hydrogen  flame  the 
spectrum  was  also  continuous.  Eder  (205)  has  also  measured  the 

1  Gmelin  and  Kraut.    Handbuch  der  anorg.  Chem.  Bd.  VI,  p.  7. 


30  ZIRCONIUM  AND  ITS  COMPOUNDS 

lines  in  the  red  and  infra-red.  Du  Bois  (86)  has  studied  the  selective 
absorption  and  the  Zeeman  effect.  Moseley  (506)  has  recorded  the 
high-frequency  spectrum. 

Chemical  Conduct.  1.  Towards  other  elements.  According  to 
Wedekind  (785),  amorphous  zirconium  when  heated  below  700°  ab- 
sorbs hydrogen,  combining  with  it  to  form  a  solid  hydride  which  is 
fully  dissociated  at  800°.  It  combines  readily  with  oxygen,  burning 
with  brilliant  light  when  heated  considerably  below  red  heat.  The 
denser  and  much  purer  metal,  however,  was  only  slowly  oxidized 
(789)  when  heated  in  air  up  to  270°.  Towards  nitrogen  amorphous 
zirconium  shows  a  like  readiness  of  combination,  forming  a  nitride. 
The  formation  of  this  nitride  is  reported  by  several  investigators 
when,  in  preparing  the  metal,  the  product  was  heated  in  the  presence 
of  air.  At  high  temperatures  (700°-1000°)  zirconium  does  not  com- 
bine with  hydrogen  or  nitrogen,  the  temperature  being  above  that  for 
dissociation  of  the  compounds.  The  oxide  is  stable  at  very  high 
temperatures.  When  the  metal  is  heated  with  carbon  a  carbide  is 
formed,  which  if  rich  in  carbon  is  gradually  decomposed  in  air  but 
otherwise  seems  stable.  Zirconium  readily  combines  at  high  tem- 
peratures with  silicon  and  boron.  With  copper,  silver,  aluminum,  and 
metals  of  the  iron  group  and  some  other  metals  alloys  are  formed,  but 
not  with  lead  or  tin  (467) .  Chlorine  and  bromine  act  upon  zirconium 
when  heated,  forming  the  tetrahalides.  Ammonia  passed  over  heated 
zirconium  gives  the  nitride.  Sulphur  also  combines  with  the  metal 
when  heated.  Red  phosphorus  gives  a  black  powder. 

2.  Behavior  towards  hydroxides  and  oxides.  When  heated  with 
alkali  hydroxides  hydrogen  is  evolved,  according  to  Troost  (714),  but 
this  action  takes  place  only  so  long  as  water  is  present.  However, 
Wedekind  reports  solutions  of  alkali  hydroxides  to  be  without  action 
(789).  This  discrepancy  is  doubtless  due  to  the  fact  that  Troost  did 
not  have  as  pure  a  metal.  Fused  with  alkali  hydroxides  the  action 
is  only  partial,  with  potassium  nitrate  it  is  explosive,  and  with  copper 
oxide  or  lead  oxide  it  is  very  energetic.  Other  oxides,  as  chromic, 
show  no  action  up  to  800°  (789).  Silica  is  reduced  at  a  bright  red 
heat  (776).  Boron  trioxide  and  titanic  oxide  are  also  reduced.  The 
great  affinity  of  zirconium  for  oxygen  has  suggested  its  use  as  a  reduc- 
ing agent  and  the  use  of  its  alloys  as  cleansing  agents  in  metallurgical 
operations. 

Action  of  Acids.  Hydrofluoric  acid  easily  dissolves  the  metal  in 
the  cold,  even  the  dilute  acid  acting  upon  it.  Concentrated  hydro- 


ZIRCONIUM  AND  ITS  PROPERTIES  31 

chloric  acid  acts  very  slightly  and  nitric  acid  not  at  all.  Hot  con- 
centrated sulphuric  acid  acts  energetically,  giving  off  sulphur  dioxide 
(789).  Aqua  regia  also  reacts  readily. 

Position  in  the  Periodic  System.  The  position  of  zirconium  in  the 
periodic  system  was  first  settled  by  its  analogies  with  the  elements 
of  the  fourth  group.  In  the  first  place,  there  is  the  formation  of  the 
typical  oxide,  Zr02,  and  the  occurrence  of  this  free  and  combined  with 
Si02.  Then  there  is  the  formation  of  the  tetrahalides  and  the  ready 
hydrolysis  of  the  tetrachloride.  From  vapor  density  determinations 
of  the  tetrachloride,  Deville  and  Troost  (185)  have  shown  the  for- 
mula to  be  ZrCl4  and  hence  the  valence  of  zirconium  four.  Also  the 
molecular  weight  determination  of  the  acetylacetonate  (69)  gives  the 
formula  ZrR4.  Furthermore,  there  is  the  amphoteric  reaction  of  the 
hydroxide  and  the  formation  of  zirconic  acid,  H2Zr03,  which  is  com- 
parable with  H4C03,  H2Si03,  H2Ti03,  and  H2Sn03.  These  five  ele- 
ments were  grouped  together  by  Mendeleeff  in  his  first  table  arranged 
according  to  the  atomic  weights.  By  means  of  the  high-frequency 
spectrum  Moseley  (506)  and  Friman  (235)  have  determined  the 
atomic  number  as  40,  which  confirms  the  above  arrangement  and  set- 
tles the  position  of  the  element. 

Atomic  Weight.  Determinations  of  this  constant  for  zirconium 
have  been  made  by  Berzelius  (53),  Hermann  (319),  Marignac  (468), 
Weibull  (794),  Bailey  (22),  Venable  (736),  Venable  and  Bell~(744). 
A  resume  of  these  is  given  in  the  following  table: 

No.  Anr  Atomic 

alyses  Weight 

6  89.46 

7  89.54 

8  90.63 
5  90.79 
4  90.03 
4  91.54 

10  90.81 

1  88.64 

2 


Date 

Author 

Ratio 

1.    1826 

Berzelius 

Zr(SO<)3:ZrO, 

2.    1881 

Weibull 

«          « 

3.    1889 

Bailey 

«         a 

4.    1881 

Weibull 

Zr(SeO.),:ZrO, 

5.    1860 

Marignac 

K.ZrFeiKaSO* 

6.    1860 

Marignac 

K2ZrF8:ZrO2 

7.     1898 

Venable 

ZrOCl2.3H2O:ZrO2 

8.    1844 

Hermann 

ZrCl4:? 

9.    1844 

Hermann 

2ZrOCl2:9H2O.ZrO2 

10.    1917 

Venable 

and  Bell 

ZrCU:4Ag 

13  91.76 


It  is  evident  that  the  present  uncertainty  as  to  this  fundamental 
constant  leaves  it  in  an  unsatisfactory  condition  and  more  accurate 
determinations  are  necessary.  The  figure  recommended  by  the  Inter- 
national committee  on  Atomic  Weights,  which  does  not  consider  series 
10,  is  90.6. 


32  ZIRCONIUM  AND  ITS  COMPOUNDS 

Salts  of  Zirconium 

These  fall  into  three  classes.  1.  Normal  zirconium  salts  in  which 
zirconium  is  the  metallic  cation  with  a  valence  of  four.  This  is  seen 
in  the  halides  ZrF4  and  ZrCl4,  also  in  combination  with  strong  acids, 
Zr(So4)2  and  Zr(N03)4.  In  the  preparation  of  these  water  must 
be  rigidly  excluded  on  account  of  the  ease  of  hydrolysis.  The  num- 
ber of  these  definitely  known,  outside  of  the  binary  compounds,  is 
small  and  the  existence  of  some  reported  is  open  to  question. 

2.  Zirconyl  and  basic  zirconyl  salts  where  the  cation  is  the  radical 
ZrO  (118).  These  are  the  product  of  the  hydrolysis  of  the  normal 
salts  and  form  the  much  larger  number  of  the  known  compounds  of 
this  element.  The  tendency  often  is  for  more  than  one  zirconyl  radi- 
cal to  enter  into  the  combination.  In  some  cases  the  increasing 
basicity  seems  to  have  no  definite  stopping  point,  as  is  indicated  by 
the  continuous  dissolving  of  the  hydroxide  in  solutions  of  the  sul- 
phate or  nitrate  until  a  thick,  gumlike  product  is  obtained  on  reach- 
ing the  limit  of  solubility.  In  the  case  of  organic  acids  there  are 
often  formed  basic  salts  whose  composition  depends  upon  the  con- 
centration, the  temperature,  and  the  relative  proportions  of  the  con- 
stituents added. 

In  the  preparation  of  certain  compounds  by  precipitation  methods 
it  has  been  found  that  the  precipitate  forms  sometimes  only  after  a 
considerable  lapse  of  time  or  upon  heating  the  solution.  This  is  espe- 
cially the  case  where  weak  acids,  such  as  the  organic  acids,  are  con- 
cerned. The  compounds  thus  formed  are  found  to  be  more  or  less 
highly  basic  zirconyl  salts  or  mixtures  of  such.  It  seems  reasonable 
to  infer  that  the  acid  radical  of  the  precipitant  used  forms  only  solu- 
ble compounds  with  the  less  hydrolyzed  salts  and  insoluble  ones  with 
the  more  basic.  It  is  possible  also  that  in  some  cases  these  are  not 
true  chemical  compounds  but  adsorption  compounds  in  which  the 
acid  radical  has  been  adsorbed  by  the  colloidal  hydroxide.  Some  of 
these  products  are  distinctly  gelatinous  and  can  be  washed  and  filtered 
with  difficulty.  On  the  other  hand,  some  are  granular  and  some  dis- 
tinctly crystalline.  The  hypothesis  of  colloidal  compounds  is  espe- 
cially probable  wherever  the  acid  radical  can  be  practically  removed 
or  greatly  reduced  in  amount  by  repeated  washings  of  the  precipitate, 
as  is  true  with  iodic  acid  and  some  organic  acids.  When,  however, 
analysis  reveals  the  same  basic  compound  as  being  formed  under 
varied  conditions  of  dilution,  etc.,  as  is  the  case  with  the  basic  chro- 


ZIRCONIUM  AND  ITS  PROPERTIES  33 

mate,  it  may  be  fairly  assumed  that  a  definite  chemical  compound 
has  been  formed. 

There  has  been  little  system  in  the  assignment  of  formulas  to 
the  basic  zirconyl  compounds.  Some  have  written  them  simply  in 
the  ratio  of  the  zirconia  to  the  acid  anhydride,  as  2Zr02 .  S03.  Others 
report  this  basic  zirconyl  sulphate  as  ZrO2.ZrOS04.  Perhaps  the 
most  common  formula  is  Zr203S04.  Such  formulas  fail  to  make  clear 
the  known  facts.  These  substances  are  often  gelatinous  and,  when 
hydrolysis  is  far  advanced,  the  solutions  become  opalescent.  On 
dialyzing  the  solutions  leave  zirconyl  hydroxide  as  a  hydrogel.  Even 
the  crystalline  basic  salts  dialyze  with  difficulty  and  show  partly  col- 
loidal properties.  They  have  been  called  half-colloids.  Electrolytic 
dissociation  shows  often  a  migration  of  the  zirconyl  radical  as  an 
anion  or  a  distribution  of  the  zirconium  between  the  anions  and 
cations.  It  is  well  known  that  the  migration  of  a  colloid  is  largely 
influenced  by  the  medium.  Furthermore,  there  is  practically  always 
water  of  hydration  or  crystallization  present.  Considering  these 
facts,  it  is  suggested  that  the  most  suitable  formula  for  these 
basic  salts  would  have  to  include  the  zirconyl  hydroxide.  Thus 
Zr02.ZrO.S04  becomes  ZrO(OH)2.ZrOS04  and  Zr203Cl2  becomes 
ZrO(OH)2.ZrOCl2.  This  reveals  at  a  glance  the  stepwise  formation 

of  the  colloid  and  the  liberation  of  the  acid,  e.g.,  ZrCl  4  +  H20 > 

ZrOCl2  +  2HCl;  2ZrOCl2  +  2H2O  -  ->  ZrO(OH)2.ZrOCl2  +  2HC1. 
Where  several  molecules  of  ZrOCl2  are  hydrolyzed  at  one  step  more 
complex  products  will  result.  This  method  of  writing  the  formulas 
has  therefore  been  adopted  throughout  this  text  wherever  accurate 
knowledge  of  the  composition  of  the  substance  was  available. 

3.  Zirconates.  Zirconyl  hydroxide  ZrO(OH)2,  which  may  be 
written  H2Zr03,  here  functions  as  an  acid  and  is  called  zirconic  acid. 
It  combines  with  strong  bases,  giving  zirconates  as  Na2Zr03.  CaZrO3, 
etc. 

Valence 

While  zirconium  is  quadrivalent  in  all  of  its  well-recognized  com- 
pounds, a  possible  hydride  has  been  reported  (67)  which  may  have 
the  composition  ZrH2.  The  existence  of  a  monoxide  ZrO,  which  would 
also  be  bivalent,  has  been  maintained  by  some  investigators,  but  the 
evidence  for  it  is  not  satisfactory. 


Chapter  III 

Compounds  of  Zirconium  with  the  Elements 
Zirconium  and  Hydrogen 

Zirconium  Hydride.  The  formation  of  a  gaseous  zirconium  hy- 
dride with  a  supposed  composition  corresponding  to  the  formula  ZrH4 
has  been  reported  but  on  insufficient  evidence  and  without  analytical 
data.  Later  work  seems  to  disprove  the  existence  of  such  a  com- 
pound. 

Winkler  (817,  818)  prepared  a  hydride  during  the  reduction  of 
zirconia  by  magnesium  in  a  stream  of  hydrogen.  The  product  was 
cooled  under  hydrogen  and  heated  again  in  an  atmosphere  of  hydro- 
gen. On  treating  with  dilute  hydrochloric  acid  abundant  hydrogen 
was  obtained  by  the  action  of  the-  acid  on  unchanged  magnesium.  A 
peculiar,  disagreeable  odor  was  noted.  The  gas  also  gave  with  silver 
nitrate  solution  a  dark  precipitate  in  which  no  zirconium  was  de- 
tected. The  product  left  after  freeing  from  magnesium  was  a  black 
powder,  unattacked  by  ordinary  reagents,  easily  filtered,  but  giving 
a  colloidal  solution  on  washing.  It  was  readily  oxidized  after  drying. 
Analyses  of  several  samples  showed  it  to  be  a  mixture  of  zirconia 
and  the  metal  or  hydride  with  an  average  of  0.73  p.c.  of  hydrogen. 
Matignon  (469)  observed  the  absorption  of  hydrogen  by  zirconium 
when  heated  and  concluded  that  a  hydride  had  been  formed. 

Wedekind  (773)  noticed  that  a  gas  was  liberated  when  the  product 
obtained  by  reducing  zirconia  with  boron  was  treated  with  dilute 
hydrochloric  acid.  It  had  an  unpleasant  smell,  blackened  paper 
moistened  with  silver  nitrite  and  burned  with  an  almost  colorless 
flame.  He  came  to  the  conclusion  that  the  gas  was  hydrogen  mixed 
with  a  small  amount  of  boron  hydride. 

Wedekind  (785)  also  analyzed  a  commercial  product  which  was 
claimed  to  be  ZrH4.  It  was  a  soft,  grayish-black  powder,  burning 
with  the  formation  of  water  and  yielding  analytical  results  which 
agreed  with  the  formula  ZrH2.  He  also  prepared  this  hydride  by 
heating  metallic  zirconium  in  a  Heraeus  furnace  filled  with  hydrogen 

34 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       35 

under  a  pressure  of  one-half  atmosphere.  The  temperature  was  car- 
ried up  to  700°  and  then  slowly  lowered.  The  hydrogen  may  be  en- 
tirely driven  off  above  800°.  The  dissociation  temperature,  therefore, 
lies  between  700°  and  800°.  The  evidence  seems  to  be  against  this  be- 
ing merely  absorbed  hydrogen  and  such  as  to  admit  of  the  conclusion 
that  zirconium  forms  a  definite  hydride  in  which  it  is  bivalent.  This 
would  correspond  with  the  known  hydrides  in  the  fourth  group,  TiH2, 
LaH2,  and  ThH2,  though  some  of  these  may  also  require  further  proof 
of  their  existence,  but  the  existence  of  such  a  compound  lacks  con- 
firmation. 

Zirconium  and  Oxygen 

Zirconium  Oxide.    The  only  definitely  known  oxide  of  zirconium 
is  the  dioxide  or  zirconia,  Zr02,  corresponding  to  C02,  Si02,  Ti02, 
and  the  oxides  formed  by  the  other  members  of  the  fourth  group. 
There  is  no  satisfactory  evidence  of  the  existence  of  a  suboxide,  ZrO. 
Certainly  no  such  oxide  has  been  prepared  or  separated,  though  sev- 
eral investigators  have  inferred  its  existence  in  order  to  explain  ob- 
servations made  by  them.    For  instance,  the  readiness  with  which 
the  metal,  as  prepared  by  the  magnesium  reduction,  oxidizes  when 
exposed  to  the  air  has  been  assumed  as  due  to  the  presence  of  this 
monoxide,  but  a  pyrophoric  condition  is  not  unusual  with  metals  in  a 
state  of  fine  subdivision.    Also  the  increase  in  weight  when  oxidized 
has  been  taken  as  a  measure  of  the  total  oxygen  present  in  combina- 
tion and  from  this  a  formula  ZrO  calculated  (767)  whereas  the  origi- 
nal product  of  the  reduction  in  preparing  the  metal  was  most  prob- 
ably a  mixture  in  unknown  proportions  of  zirconium,  zirconia,  and 
zirconium  hydroxide,  and  hence  the  data  were  insufficient  for  calcu- 
lation.   Schwarz  and  Deisler  (653)  have  shown  that  a  monoxide  is 
not  formed  by  the  reduction  of  zirconia  by  magnesium  but  a  mixture 
of  zirconia  and  the  metal  together  with  a  small  amount  of  magnesium 
zirconide.    The  migration   of  the   so-called   colloidal   zirconium,   as 
observed  by  Whitney  and  Oder  (815)  in  the  direction  of  the  negative 
stream  has  been  cited  as  a  further  argument  for  the  existence  of  ZrO, 
but  this  is  at  variance  with  the  observations  of  Wedekind    (777). 
Besides,  the  exact  nature  of  this  colloidal  zirconium  seems  to  vary 
somewhat  according  to  the  method  of  preparation  and  there  are  indi- 
cations that  at  times  zirconia  is  present,  or  rather  the  colloidal  hydrox- 
ide.   Wedekind  (780)  seems  to  have  failed  to  obtain  ZrOCl2  by  the 
chlorination   of   the   colloidal    solution   prepared    by   the   Berzelius 


36  ZIRCONIUM  AND  ITS  COMPOUNDS 

method,  which  would  be  expected  to  form  if  ZrO  were  present.  The 
oxide,  ZrO,  therefore,  is  not  known  to  exist  separately  but,  as  will  be 
seen  later,  the  radical  zirconyl  is  found  in  a  large  number  of  com- 
pounds. 

Zirconium  Dioxide.  This  oxide,  Zr02,  known  as  zirconia,  occurs 
uncombined  in  small  amounts  in  Ceylon  and  other  localities,  and  in 
commercial  quantities  in  Brazil  at  Jacupiranga,  in  the  State  of  Sao 
Paulo,  and  also  in  the  State  of  Minas  Geraes.  It  is  known  miner- 
alogically  as  baddeleyite,  and  that  which  comes  from  Brazil  as  brazil- 
ite.  The  ore  is  found  in  alluvial  pebbles  from  one-half  to  three 
inches  in  diameter,  containing  from  90  to  93  p.c.  of  zirconia.  It  is 
found  also  in  a  form  in  which  there  is  a  larger  percentage  of  zircon 
and  another  silicate  differing  from  zircon  by  its  solubility  in  hydro- 
fluoric acid.  This  ore,  a  mixture  of  brazilite,  zircon,  and  zirkelite, 
is  known  as  zirkite  and  carries  from  80  to  85  p.c.  of  zirconia.  This 
native  zirconia  contains  helium  and  argon  besides  carbon  dioxide, 
nitrogen,  oxygen,  and  hydrogen.  The  abundance  and  lesser  cost  of 
this  zirkite  make  it  the  chief  commercial  source  of  zirconia  and  the 
other  compounds.  Apart  from  this  native  zirconia  the  only  other 
practical  source  of  zirconia  is  the  zircon,  at  present  mined  only  in 
the  United  States  in  the  mountain  regions  of  North  Carolina.  This 
is  found  chiefly  in  Henderson  County  in  a  pegmatitic  dyke  which  is 
about  100  feet  wide.  The  upper  portions  of  the  dyke  are  much 
decomposed  and  kaolinized  to  a  depth  of  40  feet  or  more.  The  zir- 
cons are  well  crystallized,  easily  separated  by  hand  and  washed  free 
from  soil.  There  is  no  systematic  mining  carried  on  and  only  a  few 
tons  have  been  shipped  out. 

Purification  of  native  zirconia.  For  many  purposes  native  zir- 
conia can  be  used  without  further  treatment.  Such  uses,  for  instance, 
are  as  a  refractory  and  for  furnace  linings.  However,  for  the  prepa- 
ration of  enamels,  salts,  and  for  other  uses  requiring  purity  of  ma- 
terials the  impurities  must  be  separated.  By  fusion  with  an  alkali 
hydrogen  sulphate  and  leaching  with  water  acidulated  with  sulphuric 
acid  a  solution  of  the  sulphate  is  obtained.  Much  of  the  iron  present 
may  be  removed  by  using  a  small  amount  of  water  for  the  first  wash- 
ing and  rejecting  this.  The  solution  of  the  sulphate  yields  the  hydrox- 
ide on  the  addition  of  ammonia  solution.  This  is  dissolved  in  dilute 
hydrochloric  acid  and  the  zirconyl  chloride  purified  by  recrystalliza- 
tion  from  concentrated  hydrochloric  acid.  On  ignition  of  the  chloride 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       37 

zirconia  is  left,  but  small  amounts  of  chlorine  are  persistently  re- 
tained. 

A  more  economical  method  has  been  patented  for  large-scale  pro- 
duction (330) .  The  ore  is  heated  with  excess  of  lime  and  an  amount 
of  carbon  insufficient  for  the  reduction  of  the  lime.  Calcium  carbide 
may  be  used  in  the  place  of  the  carbon.  The  product  is  treated  with 
hydrochloric  acid,  the  silica  removed,  and  the  zirconyl  chloride  then 
purified.  Other  methods  of  preparation  are  referred  to  under  Patents. 
(See  12,  29,  250,  310,  330,  380,  444,  454.) 

Preparation  of  zirconia  from  zircons.  The  most  direct  method  is 
by  subjecting  powdered  zircons  to  the  high  temperature  of  the  electric 
furnace.  The  silica  and  oxides  of  iron  and  certain  other  metals  are 
volatilized  and  the  zirconia  is  left  in  quite  a  pure  condition.  This 
method  was  first  suggested  by  Troost  (715) .  There  is  loss  of  zirconia 
by  volatilization  at  a  very  high  temperature. 

Finely  powdered  zircon  can  be  brought  into  solution  by  fusion. 
A  number  of  different  fluxes  have  been  utilized.  Marignac  (468) 
prepared  the  fluoride  by  fusing  powdered  zircon  with  an  excess  of 
potassium  hydrogen  fluoride.  The  melted  mass  was  allowed  to  cool, 
powdered,  boiled  with  water  to  which  some  hydrofluoric  acid  had 
been  added,  and  the  potassium  fluozirconate  crystallized  out.  On  the 
addition  of  sulphuric  acid,  evaporating  to  dryness,  and  igniting 
strongly  there  was  obtained  a  mixture  of  zirconia  and  potassium  sul- 
phate from  which  the  latter  could  be  removed  by  leaching  with  water. 
Or,  as  recommended  by  Hornberger  (324),  the  evaporation  can  be 
carried  to  a  point  at  which  all  of  the  hydrofluoric  acid  and  most  of 
the  sulphuric  acid  have  been  driven  off,  then  dissolved  in  water,  and 
precipitated  by  ammonium  hydroxide. 

A  more  satisfactory  method  (733)  is  to  fuse  in  a  nickel  crucible 
400  grams  of  NaOH,  20  grams  of  Na2F2,  and  100  grams  of  powdered 
zircon  which  will  pass  through  a  100-mesh  screen.  The  heat  of  an 
ordinary  burner  is  sufficient  and  the  decomposition  takes  place  in 
from  ten  to  fifteen  minutes.  The  sodium  fluoride  should  of  course 
be  well  dried.  The  sodium  hydroxide  is  first  melted  and  the  fluoride 
then  added.  After  bringing  the  melted  mass  to  a  fairly  high  tem- 
perature the  zircon  is  gradually  added.  Rapid  evolution  of  gas  fol- 
lows the  introduction  of  the  powder,  the  mass  being  kept  well  stirred 
by  a  nickel  stirrer.  Much  seems  to  depend  upon  the  reaction  being 
carried  through  rapidly  at  a  high  temperature.  The  amount  of  un- 
attacked  zircon  should  not  exceed  0.5  p.c.  The  melted  mass  is  poured 


38  ZIRCONIUM  AND  ITS  COMPOUNDS 

out  upon  pieces  of  sheet  nickel.  While  still  hot  it  is  broken  off  and 
plunged  into  hot  water.  The  sodium  zirconate  is  left  undissolved, 
though  a  negligible  portion  will  go  into  solution.  This  zirconate  is 
then  dissolved  in  dilute  hydrochloric  acid  and  evaporated  to  dryness, 
this  being  repeated  to  separate  any  silica  and  to  drive  off  such  hydro- 
fluoric acid  as  remained.  The  dried  mass  is  leached  with  dilute 
hydrochloric  acid  and  zirconium  precipitated  as  hydroxide  with  am- 
monia. This  hydroxide  is  dissolved  in  hot  concentrated  hydrochloric 
acid,  the  solution  evaporated  to  dryness  and  the  crude  zirconyl  chlo- 
ride washed  with  ether,  thus  removing  most  of  the  iron  present.  The 
iron  can  be  reduced  to  a  trace  by  the  phosgene  method  (762).  The 
zirconyl  chloride  is  then  repeatedly  crystallized  from  boiling  hydro- 
chloric acid.  This  chloride  still  retains  some  silica  which  may  be 
removed  by  dissolving  in  water  and  filtering.  Several  crystallizations 
from  water  give  a  very  pure  chloride.  For  the  complete  removal  of 
all  impurities  it  is  necessary  to  transform  this  oxychloride  into  the 
tetrachloride  and  sublime  it  repeatedly.  On  ignition  the  chloride 
yields  the  oxide,  which  retains  some,  chlorine  even  after  prolonged 
heating  at  700°-800°.  For  the  pure  oxide  it  is  necessary  to  pre- 
cipitate the  hydroxide,  wash,  and  ignite. 

Fusions  of  zircon  have  been  made  with  the  caustic  alkalies  alone 
(45,  202,  480) ;  also  alkali  carbonates  (45,  808) ;  also  potassium 
hydrogen  sulphate.  Stolba  (683)  decomposed  zircon  by  heating  with 
a  solution  of  sodium  hydroxide  under  pressure.  By  heating  zircon 
in  the  electric  furnace  with  carbon,  or  better,  lime  and  carbon,  the 
carbide  is  formed.  This  can  be  dissolved  in  aqua  regia  and  zirconium 
hydroxide  precipitated  by  means  of  ammonium  hydroxide  (585,  792). 
The  yield  is  reported  as  only  fair. 

Crystallized  zirconia  can  be  prepared  by  the  action  of  boric  acid 
upon  zirconium  tetrafluoride  heated  in  a  carbon  crucible.  The  reac- 
tion is  3ZrF4  +  2B203  =  3Zr02  +  4BF3.  The  boron  fluoride  is  vola- 
tilized and  the  zirconia  is  left  in  the  form  of  dendritic  crystals  resem- 
bling those  of  ammonium  chloride  (184).  It  has  also  been  prepared 
quite  pure  as  white  tetragonal  crystals  by  dissolving  zirconia  in  melted 
magnesium  chloride.  The  crystals  separated  out  on  cooling  (346) 
as  white  tetragonal  prisms  and  had  a  density  of  5.74.  Moissan  (500) 
obtained  a  vitreous  crystalline  mass  showing  dendritic  form  on  frac- 
ture by  bringing  zirconia  to  full  boiling  in  an  electric  furnace  by 
means  of  a  current  of  360  amperes  and  70  volts.  Abundant  vapors 
of  zirconia  also  came  off.  The  form  of  zirconia  crystals  has  also 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       39 

been  reported  (586)  as  quadratic  and  hexagonal.  Berzelius  reports 
zirconia  as  dimorphous.  It  has  been  reported  as  isomorphic  with 
silica.  Native  zirconia,  baddeleyite,  is  monoclinic,  often  twinned, 
and  with  perfect  cleavage.  It  has  a  negative  double  refraction,  a 
density  of  5.41,  and  hardness  of  6  to  7  (360,  361). 

Properties.  The  heat  of  formation  of  zirconia  by  direct  oxidation 
of  the  metal  is:  Zr+02  =  Zr02+  1958.7  cal.  (498).  It  forms  a 
white,  impalpable  powder  which  is  easily  swept  away  in  the  process 
of  ignition;  also  a  rough,  coarse  powder  which  is  hard  to  crush  com- 
pletely and  scratches  glass.  If  prepared  by  the  gradual  dehydration 
of  the  hydroxide  and  then  raising  the  temperature  to  800°-1000°  it 
forms  a  compact,  semi-vitrified  mass.  The  density  has  been  vari- 
ously reported  as  5.45,  Hermann;  5.50,  Sjogren;  5.49,  Venable  and 
Belden;  5.85,  Nilson  and  Petterson;  5.66,  Ruer;  5.89,  Bradford.  The 
melting  point  has  been  given  as  2563°  at  30  mm.  pressure  (626),  2700° 
(762),  and  2950°  (97),  and  is  next  to  the  highest  melting  point  for 
any  metallic  oxide.  The  melting  point  of  MgO  is  2800°.  The  specific 
heat  is  0.1076  (533)  and  it  is  diamagnetic  (5).  It  melts  and  is  volatil- 
ized in  an  electric  furnace,  and  the  melting  point  and  beginning  of 
vaporization  are  said  to  lie  quite  close  together.  The  boiling  and 
vaporization  can  be  readily  observed.  This  boiling  point  has  been  fixed 
by  Mott  (509)  at  4300°.  The  coefficient  of  expansion  is  low,  namely, 
0.00000084,  about  the  same  order  as  that  of  silica.  The  conductivity 
for  heat  and  electricity  is  also  low.  The  porosity  is  low  (under  1  p.c.) 
and  vessels  made  of  it  are  impervious  to  most  liquids.  When  heated 
in  the  oxy-hydrogen  flame  it  gives  off  a  very  brilliant  light  with 
comparatively  little  heat  and  yields  a  continuous  spectrum.  Cob- 
lentz  (1,47)  has  investigated  the  diffuse  reflecting  power  of  zirconia. 

Chemical  Conduct.  Early  attempts  to  reduce  zirconia  failed  (170, 
711).  It  is  partially  reduced  on  ignition  in  a  reducing  flame  (29). 
Dissociation  begins  at  about  2500°.  Ordinary  reducing  agents, 
such  as  hydrogen,  do  not  have  any  action  upon  it.  Its  reduction  in 
the  electric  furnace  by  means  of  carbon  begins  at  1400°,  a  carbide 
being  formed  (257).  Boron  and  silicon  also  reduce  it,  forming 
respectively  a  boride  and  silicide  (723,  791).  Various  metals, 
such  as  aluminium  and  magnesium,  also  reduce  zirconia,  partly 
alloying  with  the  metal.  Various  agents,  such  as  carbon  tetrachloride 
and  carbonyl  chloride,  bring  about  double  decomposition,  forming  the 
tetrachloride  and  carbon  dioxide. 

When  mixed  with  carbon  and  heated  zirconia  is  acted  upon  by 


40  ZIRCONIUM  AND  ITS  COMPOUNDS 

chlorine  and  bromine  with  the  formation  of  the  tetrachloride  and 
tetrabromide.  It  is  also  acted  upon  by  phosphorus  pentachloride 
when  heated  in  a  closed  tube.  When  a  mixture  of  chlorine  and  carbon 
tetrachloride  is  passed  over  zirconia  heated  to  300°-400°  zirconium 
tetrachloride  is  formed. 

When  zirconia  is  ignited  it  becomes  practically  insoluble  in  all 
acids  except  hydrofluoric.  The  discrepancies  in  the  statements  as  to 
its  solubility  in  other  acids  seem  to  be  due  to  differences  in  the  degree 
of  ignition. 

Zirconia  is  readily  dissolved  in  melted  caustic  alkalies  with  the 
formation  of  zirconates.  When  added  to  melted  alkali  carbonates 
carbon  dioxide  is  evolved,  but  the  formation  of  zirconates  is  more 
difficult  and  only  partial.  Melting  with  certain  chlorides  also  yields 
zirconates.  When  melted  with  the  bisulphates  soluble  salts  or  double 
salts  are  obtained.  Those  with  potassium  are  more  difficultly  soluble. 
It  is  not  dissolved  in  melted  boric  acid  (747) . 

Zirconium  and  Hydrogen  and  Oxygen 

Zirconium  Hydroxide.  This  is  usually  prepared  by  precipitation 
from  a  solution  of  a  zirconyl  salt.  When  an  alkali  hydroxide  is  used 
it  is  almost  impossible  to  wash  the  precipitate  entirely  free  from  the 
alkali.  Even  when  ammonia  is  used  prolonged  washing  is  necessary 
in  order  to  secure  the  pure  hydroxide.  The  precipitated  hydroxide 
is  bulky  and  gelatinous,  resembling  aluminum  hydroxide.  On  dry- 
ing it  forms  a  semi-opaque,  vitreous  mass,  cracking  and  breaking  up 
on  shrinking.  After  draining  on  the  filter  it  retains  as  much  as 
95  p.c.  of  water;  air-dried,  the  water  content  is  47  p.c.  (42) ;  dried  in 
vacuo,  there  is  still  left  about  20  p.c.  of  water  (171,  536).  After 
several  weeks'  standing  over  sulphuric  acid  the  weight  becomes  nearly 
constant.  The  water  content  was  found  to  be  22.89  and  23.01  p.c. 
(326,  466).  In  these  experiments  the  precipitation  and  washing  took 
place  in  the  cold  and  evidently  normal  hydroxide  was  obtained  when 
dried  over  sulphuric  acid.  The  calculated  percentage  of  water  for 
Zr(OH)4  is  22.69.  By  washing  the  fresh  precipitate  once  with  alcohol 
and  then  ether  the  percentage  of  water  was  reduced  to  26.50;  wash- 
ing with  petroleum  ether  the  water  was  reduced  to  26.44,  a  mean  of 
several  experiments  (743). 

Dried  at  100°,  whether  precipitated  hot  or  cold,  the  compound 
ZrO(OH)?  is  left  (50,  537,  466).  This  partial  dehydration  takes 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       41 

place  in  the  hot  precipitation  when  the  solution  is  heated  to  85°  or 
over  (42),  the  precipitate  being  dried  at  100°  (50)  or  140°  or  higher 
(42),  representing  then  a  fairly  stable  compound.  This  is  the  zir- 
conyl  hydrate.  Van  Bemmelen  reports  that  there  is  no  further  loss 
of  water  up  to  200°.  At  300°  something  over  one-half  p.c.  of  water 
is  left  and  the  last  traces  of  water  can  be  removed  only  by  heating 
to  a  much  higher  temperature.  The  addition  of  water  does  not  restore 
water  of  hydration  to  the  once  partially  dehydrated  hydroxide. 

The  earlier  observation  (171)  that  after  all  water  had  been  re- 
moved and  the  oxide  was  further  heated  there  was  a  sudden  loss  of 
potential  energy  with  emission  of  light  has  been  partially  confirmed 
and  the  conditions  more  accurately  fixed,  it  having  been  reported  that 
sometimes  the  phenomenon  failed  to  appear  (42,  600).  The  light 
appears  at  about  300°,  but  only  when  the  hydroxide  has  been  par- 
tially dehydrated  at  a  somewhat  lower  temperature,  retaining  a  small 
fraction  of  the  water  (less  than  1.9  p.c.).  The  heat  of  this  change, 
ZrO(OH)2  =  Zr02  +  H20,  is  about  9.2  cal.  to  the  gram  of  zirconia. 
When  heated  higher  there  are  sudden  small  explosions  with  the  pro- 
duction of  extremely  fine  powder  (619).  This  doubtless  partly  ac- 
counts for  the  loss  of  zirconia  in  quantitative  determinations  even 
under  all  the  usual  precautionary  conditions. 

The  normal  Zr(OH)4,  or  cold  precipitated  hydroxide,  is  practically 
insoluble  in  water.  It  is  readily  dissolved  by  concentrated  or  dilute 
inorganic  acids  to  form  salts  though  only  sparingly  soluble  in  hydri- 
odic.  Among  the  organic  acids  oxalic  is  the  most  reactive,  dissolving 
it  nearly  as  rapidly  as  some  of  the  inorganic  acids.  Saturated  solu- 
tions of  tartaric  and  citric  acids  and  glacial  acetic  acid  dissolve  very 
little  (743). 

Zirconyl  hydroxide,  ZrO(OH)2,  which  is  precipitated  from  hot 
solutions,  is  more  slowly  soluble  in  dilute  inorganic  acids,  dilute  hydro- 
chloric or  dilute  nitric  acid  dissolving  only  about  1:100,  and  dilute 
oxalic  acid  about  half  as  much..  If,  however,  the  precipitate  stands 
for  some  days  in  contact  with  the  acid  it  is  dissolved  to  about  the 
same  extent  as  when  precipitated  cold  (743).  The  chief  difference 
noted  in  the  case  of  concentrated  acids  is  that  some  act  more  slowly. 

Ammonia  (Sp.  Gr.  0.9)  does  not  seem  to  dissolve  the  hydroxide 
appreciably.  When  diluted  it  dissolves  about  1:10,000.  Potassium 
or  sodium  hydroxide  have  a  decidedly  greater  solvent  action,  espe- 
cially the  latter.  Presumably  a  compound  is  first  formed  which  is 
then  dissolved.  If  a  concentrated  solution  of  an  alkali  hydroxide 


42  ZIRCONIUM  AND  ITS  COMPOUNDS 

saturated  with  zirconium  hydroxide  is  diluted  a  portion  of  the  hy- 
droxide will  be  precipitated,  probably  as  zirconate  (747).  Certain 
salts  of  ammonia  exert  a  greater  solvent  action  than  the  hydroxide. 
A  saturated  solution  of  the  commercial  carbonate  dissolves  about 
1 : 100  and  an  ammoniacal  solution  of  ammonium  tartrate  has  a  some- 
what lesser  action.  The  density  of  the  hydroxide  precipitated  cold 
and  containing  25.97  p.c.  of  water  is  3.25  (743). 

Colloidal  Zirconium  Hydroxide.  This  colloid  has  been  prepared 
by  the  dialysis  of  a  zirconyl  nitrate  solution.  The  liquid  appears 
clear  in  transmitted  light  but  cloudy  in  reflected  and  contains  1.98 
grams  of  zirconia  to  the  100  c.c.  It  is  stable  when  boiled  and  fairly 
stable  towards  electrolytes.  The  hydrosol  is  positively  charged  (67, 
68).  Also  by  the  dialysis  of  a  zirconyl  chloride  solution  a  colloidal 
hydroxide  has  been  obtained  (0.6  gram  zirconia  in  100  c.c.)  which 
was  clear  in  both  transmitted  and  reflected  light.  The  hydrosol  re- 
tains some  chlorine  which  is  not  directly  precipitated  by  silver  nitrate 
but  is  protected  by  the  colloid.  On  attempting  to  remove  the  last 
of  the  chlorine  a  hydrogel  is  formed.  The  chlorine  can  be  precipitated 
after  boiling  with  nitric  acid.  A  largely  hydrolyzed  zirconium  oxy- 
chloride  containing  5.5  p.c.  chlorine  and  87  p.c.  zirconia  yields  in  water 
a  milky  solution  in  which  acids  give  a  precipitate.  A  colloid  can  be 
prepared  from  this  solution  nearly  free  from  chlorine.  The  colloidal 
hydroxide  is  precipitated  by  such  electrolytes  as  sodium  or  ammonium 
chloride  (619). 

A  colloidal  hydroxide  has  also  been  prepared  by  boiling  a  highly 
basic  zirconium  nitrate  with  water  and  filtering.  The  hydrosol  is 
opalescent  and  on  evaporation  yields  a  gummy  residue  which  swells 
and  dissolves  in  water.  Slightly  ionizing  univalent  salts  have  no 
effect  upon  this  hydrosol,  but  strongly  ionizing  salts  cause  coagula- 
tion. Anions  of  a  higher  valence  cause  precipitation.  The  valence 
of  the  cation  is  a  negligible  factor  (512).  The  dialysis  of  a  1.5  p.c. 
solution  of  zirconium  acetate  gives  a  clear  colloidal  solution  containing 
0.45  grams  of  zirconia  to  the  100  c.c.  and  very  little  acetic  acid.  To- 
wards electrolytes  it  behaves  in  the  same  manner  as  the  preparation 
just  described  (611).  By  peptonizing  zirconium  hydroxide  with 
uranyl  nitrate  a  yellowish,  milky,  strongly  opalescent,  very  stable 
colloidal  solution  is  obtained  (695). 

It  would  seem  that  in  preparing  the  colloid  from  these  hydrolyzed 
and  highly  basic  compounds  some  of  the  surplus  of  zirconium  hydrox- 
ide is  separated  from  the  salt.  Lottermoser  (445),  who  apparently 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       43 

used  a  less  hydrolyzed  solution,  failed  to  secure  a  hydrosol.  Van 
Bemmelen  (42)  advanced  the  theory  that  the  zirconium  hydroxide 
forms  in  these  highly  basic  salts  an  adsorption  compound  with  the 
zirconyl  salt.  It  will  be  seen  later  that  the  hydrolysis  progresses  in 
a  far-reaching  manner,  though  halting  places  are  observed  where 
definite  compounds  seem  to  be  formed.  Mliller  (512)  has  suggested 
that  opalescent  or  non-opalescent  dilute  solutions  of  zirconyl  hydrox- 
ide in  salts  of  zirconium  are  to  be  looked  upon  not  as  basic  but  as 
adsorption  compounds  of  the  colloidal  hydroxide  with  the  salt.  These 
salts  then  yield  colloidal  solutions  and  in  all  of  them  a  hydrogel  is 
present.  The  adsorptive  power  of  zirconium  is  very  considerable 
and  comparable  with  that  of  aluminum  hydroxide.  On  this  account 
its  utilization  has  been  proposed  in  the  purification  of  water,  mor- 
danting of  textiles,  preparation  of  lac  dyes,  and  for  similar  purposes. 
Hydrolysis  and  formation  of  zirconyl  hydroxide.  All  salts  of 
zirconium  hydrolyze  very  readily  when  dissolved  in  water  with  the 
separation  of  free  acid  and  zirconyl  hydroxide.  Salts  of  quadrivalent 
zirconium  do  not  exist  in  aqueous  solution.  In  such  solutions  the 
bivalent  zirconyl  radical  is  always  present.  This  forms  a  weak  base 
and  is  amphoteric.  Definite  proof  as  to  the  formation  of  this  hydrox- 
ide is  not  always  available,  but  the  ease  with  which  the  normal 
hydroxide  is  itself  dehydrated,  especially  in  even  moderately  warm 
water,  and  other  facts  render  this  probable.  In  some  cases  the  zir- 
conyl hydroxide  has  been  separated  by  dialysis.  When  the  acid  is 
volatile  it  is  easily  lost  on  evaporation  or  when  the  solution  is  set 
aside  over  a  caustic  alkali  absorbent.  The  hydrolysis  is  often  pro- 
gressive so  that  the  acid  constituent  may  be  largely  washed  away  from 
a  precipitated  insoluble  basic  salt.  In  a  number  of  instances  the  in- 
soluble basic  compound  is  formed  only  after  prolonged  standing  of 
the  solution.  This  precipitation  may  be  hastened  by  boiling  the  solu- 
tion. This  may  indicate  a  progressive  hydrolysis,  the  normal  hydrox- 
ide being  first  formed  and  then  dissociated  into  zirconyl  hydroxide 
and  water,  the  insoluble  basic  salt  being  a  compound  of  zirconyl 
hydroxide.  This  being  the  most  plausible  assumption,  the  basic  salts 
to  be  described  later  will  have  formulas  ascribed  to  them  as  com- 
pounds of  zirconyl  hydroxide.  Many  of  these  basic  compounds  form 
crystals  whose  composition  can  be  definitely  determined  or  precipi- 
tates in  which  the  composition  is  little  changed  by  repeated  washings. 
Some  form  neither  crystals  nor  precipitates  but  leave  a  gummy  mass 
on  evaporation.  In  such  masses  indications  of  crystalline  structure 


44  ZIRCONIUM  AND  ITS  COMPOUNDS 

are  sometimes  to  be  found.  The  custom  has  often  been  followed  of 
reporting  the  basic  compounds  with  formulas  containing  Zr02.  There 
would  seem  to  be  little  justification  for  the  use  of  this  or  of  the  easily 
dehydrated  Zr(OH)4.  Some  of  the  salts  would  seem  to  be  adsorption 
compounds  with  colloidal  ZrO(OH)2  and  lacking  in  definite  composi- 
tion. 

On  heating  a  zirconium  salt  of  a  volatile  acid,  such  as  hydrochloric 
or  sulphuric,  to  a  temperature  of  500°  to  800°  most  of  the  acid  is 
eliminated  but.  traces  of  these  acids  are  held  even  after  prolonged 
ignition  (744) .  The  amount  retained  is  ordinarily  too  small  to  inter- 
fere materially  with  analytical  results. 

Higher  Oxides  of  Zirconium.  1.  Zr03  was  obtained  in  the  hy- 
drated  form  as  a  white  precipitate  by  Cleve  (146)  on  adding  hydrogen 
peroxide  to  a  solution  of  zirconium  sulphate  made  alkaline  by  am- 
monium hydroxide.  The  precipitate  was  dried  over  sulphuric  acid 
and  potassium  hydroxide  and  gave  on  analysis  13.12  p.c.  of  oxygen 
in  excess  of  Zr02,  which  corresponds  closely  with  the  amount  calcu- 
lated for  Zr03.  Bailey  (22)  on  repeating  this  experiment  used  an 
acid  solution  so  as  to  avoid  the  possible  presence  of  zirconium  hydrox- 
ide from  the  excess  of  ammonia.  He  also  obtained  a  bulky,  white 
precipitate  which,  on  being  heated  gently  with  hydrochloric  acid  and 
potassium  iodide,  liberated  iodine.  This  precipitate,  after  thorough 
washing,  was  allowed  to  stand  three  months.  The  analysis  yielded 
69.46  p.c.  of  zirconium  and  30.54  p.c.  of  oxygen.  A  freshly  precipi- 
tated preparation  gave  closely  concordant  results.  These  correspond 
with  the  formula  Zr205.  Further  determinations  of  the  combined 
water  gave  the  complete  formula  as  Zr205.4H20.  This  is  partially 
dissociated  on  boiling  and  is  insoluble  in  dilute  sulphuric  and  acetic 
acids.  From  more  dilute  solutions  the  precipitate  corresponded  to 
ZrO3.5H20.  If  this  is  dried  at  100°  the  analysis  corresponds  with 
Zr03  (22). 

Piccini  (549)  failed  to  get  such  precipitates.  It  has  been  sug- 
gested (238)  that  the  solutions  used  by  him  were  too  dilute  and  that 
the  compound  Zr205  obtained  by  Bailey  was  perhaps  a  decomposition 
product.  Geisow  (238)  also  confirmed  the  results  of  Cleve,  using  a  30 
per  cent  solution  of  hydrogen  peroxide  and  precipitating  in  solution 
made  alkaline.  Pissarjewski  (554) ,  who  prepared  Zr03  (hydrated)  by 
precipitation  with  H202  in  an  ammoniacal  solution  at  a  temperature 
of  0°  to  3°,  stated  that  the  trioxide  loses  active  oxygen  on  standing 
and  that  it  is  entirely  lost  at  75°.  The  heat  of  formation  is  given  as 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       45 

-21.786  cal.  The  formation  of  this  precipitate  with  hydrogen  per- 
oxide has  been  recommended  as  a  means  of  quantitative  separation 
of  zirconium  from  iron  (238,  775). 

The  trioxide  has  also  been  prepared  by  the  action  of  hydrogen 
peroxide  on  an  alkali  tartrate  solution  (775,  293) ;  by  its  action  upon 
zirconyl  hydroxide  or  the  action  of  sodium  hypochlorite  on  zirconyl 
nitrate  at  8°-10°;  and  by  the  electrolysis  of  an  alkaline  solution  of 
sodium  chloride  in  which  zirconyl  chloride  is  suspended  (549).  It 
forms  a  gelatinous  precipitate  which  is  decomposed  on  standing  over 
sulphuric  acid  or  soda  lime. 

Zirconium  and  Nitrogen 

Zirconium  Nitride.  Zirconium  shows  a  strong  affinity  for  nitro- 
gen. The  metal  readily  combines  with  it  when  heated  in  a  stream 
of  nitrogen  or  when  heated  in  the  air.  Thus  the  earlier  attempts  at 
preparing  zirconium  yielded  products  containing  the  nitride,  as  air 
was  not  rigidly  excluded.  On  exclusion  of  nitrogen  no  nitride  was 
formed  (818).  The  evidence  as  to  the  presence  of  nitride  was  the 
formation  of  ammonia  on  treatment  with  a  caustic  alkali.  When  the 
carbide  is  heated  in  nitrogen  the  carbon  is  displaced  and  a  nitride 
formed  (779).  The  nitrides  heated  in  a  stream  of  hydrogen  yield 
ammonia  and  the  metal  (473). 

The  formation  of  the  nitride  was  observed  by  Wohler  (820) 
in  1839.  In  1859  Mallet  (463)  in  attempting  to  prepare  zirco- 
nium by  the  reduction  of  the  oxide  with  aluminum  in  a  lime  crucible, 
which  cracked,  obtained  a  product  which  on  treating  with  hydrochloric 
acid  left  undissolved  iron-black,  lustrous  leaflets  and  a  golden-colored 
substance.  The  latter  was  in  the  form  of  microscopic  cubes  which 
were  slightly  attacked  by  acids  and  caustic  alkalies  and  showed  a 
slight  formation  of  ammonia  when  left  under  water.  By  heating 
amorphous  zirconium  in  a  stream  of  ammonia  until  the  glass  tube 
softened  he  obtained  a  product  which  gave  off  ammonia  abundantly 
when  fused  with  caustic  alkali.  Heated  in  the  air  it  burned  to  zir- 
conia.  A  similar  product  was  prepared  by  heating  zirconium  chloride 
in  a  stream  of  ammonia.  Zirconium  heated  in  a  stream  of  cyanogen 
gave  a  dark,  amorphous  powder  which  gave  off  ammonia  abundantly 
on  fusion  with  caustic  alkali  and  burned  to  a  white  powder  in  air. 
He  believed  the  cyanogen  formed  a  nitride  though  possibly  admixed 
with  cyanide.  No  analyses  were  reported. 


46  ZIRCONIUM  AND  ITS  COMPOUNDS 

Matthews  (473)  heated  ZrCl4.8NH3  to  redness  in  a  stream  of 
nitrogen.  Abundant  fumes  of  ammonium  chloride  were  given  off. 
The  residue,  a  pearl-gray  powder,  yielded  ammonia  when  heated  in  a 
stream  of  hydrogen.  The  nitrogen  present  was  determined  by  dis- 
solving this  gas  in  a  standard  solution  of  hydrochloric  acid.  The 
residue  was  burned  to  zirconia  and  weighed.  The  analysis  corresponds 
with  the  formula  Zr3N8.  When  ZrCl4.4NH3  was  treated  in  the  same 
way  the  analysis  of  the  product  gave  Zr2N3. 

Wedekind  (777)  found  that  when  magnesium  was  heated  in  the 
air  with  zirconia  a  greenish-brown  crystalline  powder  was  left.  This 
glowed  on  gentle  heating  and  when  scattered  in  a  flame  burned  with 
scintillations.  It  was  notably  stable  towards  acids,  excepting  hydro- 
fluoric, and  did  not  conduct  electricity.  On  fusing  with  alkalies  am- 
monia was  given  off.  The  analysis  corresponded  with  the  formula 
Zr2N3. 

Bruyere  and  Chauvenet  (110)  have  shown  that  all  ammonia  com- 
pounds with  zirconium  tetrachloride  yield  Zr(NH3)4Cl4  on  heating 
up  to  195°.  This  is  true  also  of  the  iodide.  At  higher  temperatures 
the  halogen  acid  and  not  ammonia  is  given  off.  Thus  at  225°-250° 
the  amide  Zr(NH2)4  is  formed  in  an  atmosphere  of  hydrogen  or  am- 
monia. Above  250°  the  product  seems  to  be  a  mixture  of  an  imide 
and  a  nitride,  Zr(NH)2  +  Zr3N4.  At  350°  only  the  Zr3N4  remains. 
This  is  insoluble  and  unchanged  in  water.  According  to  these  ob- 
servers the  nitride,  Zr3N8,  reported  by  Matthews  is  to  be  regarded  as 
a  mixture  of  the  amide  Zr(NH2)4  and  the  imide  Zr(NH)2. 

Wedekind  (785),  in  examining  the  properties  of  the  purest 
zirconium  he  could  obtain,  found  that  nitrogen  shows  little  action 
upon  powdered  zirconium  under  1000°.  There  is  practically  no  change 
at  500°;  at  700°  1  p.c.  is  changed;  at  800°  4  p.c.;  at  1050°  to  1080° 
9  p.c.  The  product  at  this  temperature  is  Zr3N2.  The  same  nitride 
is  given  by  ammonia  at  1000°.  It  is  a  crystalline  powder  with  metal- 
lic lustre,  more  resistant  to  oxygen  and  chlorine  than  zirconium,  with 
about  the  same  resistance  to  acids.  Solutions  of  alkalies  show  no 
action,  but  fusion  with  caustic  alkalies  yields  ammonia.  It  is  stable 
when  heated  in  a  hydrogen  stream  up  to  1000°.  It  conducts  elec- 
tricity. 

Curtius  (157)  has  stated  that  on  adding  a  solution  of  sodium 
azide  (NaN3)  to  a  solution  of  zirconium  sulphate  a  precipitate  of 
zirconium  hydroxide  is  formed  and  no  zirconium  is  left  in  the  filtrate. 
The  azide  was  not  formed  by  this  method. 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       47 

The  nitrides  reported  are  Zr3N2,  Zr2N3,  Zr3N4,  and  Zr3N8.  In 
addition  there  are  the  amide  Zr(NH2)4  and  the  imide  Zr(NH)2. 

Zirconium  and  Carbon 

Zirconium  Carbide.  The  first  observation  as  to  the  formation  of 
zirconium  carbide  was  made  by  Berzelius,  who,  in  preparing  zirconium 
by  means  of  potassium  containing  carbon,  obtained  amorphous  zir- 
conium which  left  a  residue  of  carbon  on  treatment  with  boiling  hy- 
drochloric acid  and  gave  off  an  unpleasant-smelling  gas  containing 
hydrogen. 

Troost  (714)  heated  powdered  zircon  with  carbon  in  an  electric 
furnace,  using  a  current  of  35  amperes  at  70  volts,  and  obtained 
metallic-like  masses  of  carbide.  The  analyses  indicated  the  com- 
position ZrC2  but  did  not  agree  closely  and  no  distinction  seems  to 
have  been  made  between  mixed  and  combined  carbon.  The  product 
did  not  alter  in  the  air  and  was  not  attacked  by  water  or  acids  except 
hydrofluoric.  If  little  carbon  was  used  the  product  did  not  oxidize 
at  red  heat  in  the  air.  If  much  carbon  was  used  in  its  preparation  it 
burned  brilliantly. 

Moissan  (500),  on  fusing  powdered  zirconia  in  an  electric  fur- 
nace with  an  excess  of  carbon,  prepared  a  substance  containing  4  to 
5  p.c.  of  carbon.  When  this  was  heated  with  more  zirconia  the  car- 
bon was  eliminated.  When  rich  in  carbon  it  was  rapidly  decomposed 
by  air.  Later  (501)  he  mixed  the  powdered  zirconia  with  carbon 
prepared  from  sugar,  using  oil  and  pressing  the  mass  into  a  cylinder 
which  was  then  calcined.  It  was  afterwards  subjected  to  the  action 
of  a  current  of  1000  amperes  and  50  volts.  Varying  amounts  of  car- 
bon were  used,  yielding  the  same  results.  The  product  had  a  metal- 
lic appearance  and  was  unchanged  in  moist  air  even  when  heated  to 
100°.  The  analysis  yielded  88.6  p.c.  of  zirconium  and  11.4  p.c.  of 
carbon,  which  agrees  with  the  formula  ZrC.  The  fact  that  this  com- 
position was  maintained  when  the  amount  of  carbon  used  was  varied 
brings  still  more  into  question  the  existence  of  the  ZrC2  reported  by 
Troost.  Wedekind  (785)  obtained  the  same  result  as  Moissan  by 
using  a  current  of  600  amperes,  voltage  not  given. 

The  carbide  has  a  hardness  between  7  and  9,  scratching  glass  and 
quartz,  and  its  use  as  an  abrasive  has  been  suggested.  Chlorine  acts 
upon  it  at  250°,  bromine  at  300°,  and  iodine  at  400°.  At  a  red  heat 
it  burns  in  the  air.  Sulphur  yields  a  small  amount  of  the  sulphide 


48  ZIRCONIUM  AND  ITS  COMPOUNDS 

when  heated  with  this  carbide  to  a  red  heat.  If  melted  with  carbon 
in  an  electric  furnace  carbon  is  dissolved,  the  excess  separating  as 
graphite  on  cooling.  Ammonia  and  water  are  without  action  at  a 
red  heat.  Hydrofluoric  acid  acts  readily  in  the  cold.  Boiling  hydro- 
chloric acid  has  no  action.  Nitric  acid  acts  slightly  when  dilute,  but 
the  concentrated  acid  acts  immediately  and  violently  and  so  does 
aqua  regia.  Sulphuric  acid  readily  decomposes  it  when  heated. 
Nitrates  and  permanganates  attack  it  readily,  and  chlorates  give  an 
explosive  mixture  when  heated.  Fused  caustic  potash  dissolves  it 
readily.  There  is  no  action  on  fusing  with  potassium  cyanide. 

Wedekind  (779)  prepared  a  carbide  from  native  zirconia  by  mixing 
the  finely-ground  powder  with  carbon  and  heating  in  an  electric  fur- 
nace. The  product  sintered  into  a  metallic-like  mass  which  was  stable 
in  air,  water,  and  hydrochloric  acid  but  was  decomposed  by  chlorine 
at  300°.  It  was  found  to  contain  a  small  percentage  of  iron  oxide, 
silica,  and  silicates.  After  deducting  this  the  analysis  agreed  well 
with  the  formula  ZrC.  It  is  a  good  conductor  of  electricity  and  its 
use  for  electrodes  has  been  suggested.  As  anode  it  would  be  quickly 
attacked  by  oxygen.  When  heated  to  a  red  heat  in  a  stream  of 
nitrogen  a  nitride  was  formed.  Mott  (509)  has  given  the  boiling 
point  of  the  carbide  as  5100°. 


Zirconium  and  Sulphur 

Zirconium  Sulphide.  The  sulphide  was  first  prepared  by  Ber- 
zelius  (53)  by  heating  the  metal  with  sulphur  in  a  vessel  previously 
evacuated.  When  the  two  were  heated  in  hydrogen  there  was  a  slight 
appearance  of  flame.  No  details  are  given  as  to  the  composition  of 
the  product  but  the  impurities  in  the  metal  used  would  necessarily 
render  it  impure.  The  sulphide  is  described  as  a  dark  cinnamon- 
brown  powder  which  could  not  be  polished  to  a  lustrous  appearance. 
As  will  be  seen  later,  the  pure  sulphide  is  crystalline  and  has  a  steel- 
gray  color.  When  fused  with  caustic  potash  zirconia  and  potassium 
sulphide  were  formed.  Hydrofluoric  acid  dissolved  it  easily  with  the 
evolution  of  hydrogen  sulphide.  Boiling  aqua  regia  dissolved  it  slowly. 
Hydrochloric,  nitric,  and  sulphuric  acids,  as  well  as  a  solution  of 
caustic  potash,  gave  no  reaction. 

Paykull  (536)  prepared  an  impure  sulphide  (containing  some 
oxygen)  by  subliming  zirconium  tetrachloride  in  a  stream  of  hydrogen 
sulphide,  the  presence  of  oxygen  not  being  entirely  excluded.  The 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       49 

product  was  stable  in  the  air  and  water  and  burned,  when  heated, 
with  the  formation  of  sulphur  dioxide.  It  was  oxidized  by  aqua  regia 
and  also  by  nitric  acid.  Chlorine  gave  zirconium  tetrachloride  and 
sulphur  dioxide  on  the  application  of  heat.  Moissan  and  Lengfeld 
(501)  obtained  a  small  amount  of  the  sulphide  on  heating  zirconium 
carbide  and  sulphur  to  a  dark  red  heat.  Fremy  (231),  by  the  action 
of  carbon  bisulphide  upon  zirconia  at  a  red  heat,  prepared  zirconium 
sulphide  in  the  form  of  fine,  needlelike  crystals  of  a  steel-gray  color. 
These  showed  the  characteristics  of  the  product  obtained  by  Ber- 
zelius.  They  were  not  decomposed  by  water  nor  ordinary  acids  except 
nitric  acid,  which  oxidized  the  zirconium  readily,  giving  an  abundant 
deposit  of  sulphur.  The  formula  for  the  sulphide  prepared  by  these 
methods  would  seem  to  be  ZrS2.  Hauser  (294)  repeated  the  prepara- 
tion by  the  method  of  Berzelius  by  heating  the  metal  in  the  vapor  of 
sulphur,  but  in  this  case  also  the  metal  was  not  pure. 

Zirconium  Oxysulphide.  The  oxysulphide,  ZrOS,  was  also  pre- 
pared by  Hauser  (294)  by  the  reduction  of  the  sulphate  (dried  at 
400°)  when  heated  to  a  strong  red  heat  in  a  stream  of  dry  hydrogen 
sulphide.  It  is.  a  bright  yellow  powder  with  a  density  of  4.87.  If  re- 
moved from  the  tube  before  completely  cooling  it  caught  on  fire.  The 
analysis  (Zr,  65.3  p.c.  and  S,  22.8  p.c.)  agrees  with  the  formula  ZrOS. 

Zirconium  and  Boron 

Zirconium  Boride.  The  boride  has  been  prepared  by  Tucker  and 
Moody  (723),  who  used  zirconium  gotten  by  the  reduction  of  the 
double  fluoride  of  potassium  and  zirconium  by  means  of  aluminum. 
Hence  their  results  are  impaired  by  the  presence  of  aluminum  as  an 
impurity.  Fifteen  grams  of  this  product  were  heated  with  2.2  grams 
of  boron  in  a  carbon  crucible  for  five  minutes  by  a  current  of  200  am- 
peres at  65  volts.  The  product  was  brittle,  steel-gray  in  color,  and 
under  the  microscope  appeared  as  an  agglomeration  of  brilliant,  trans- 
lucent to  transparent,  tabular  crystals  having  a  density  of  3.7  and 
a  hardness  of  8.  They  were  slowly  attacked  by  hot  concentrated  acid 
and  aqua  regia.  The  analysis  gave  86  p.c.  of  zirconium,  which  would 
point  to  the  formula  Zr3B4  if  these  two  elements  alone  were  present. 

Wedekind  (773)  tried  the  reduction  of  zirconia  by  means  of 
boron,  heating  5  grams  of  zirconia  with  1.1  grams  of  boron  in  an 
electric  furnace.  This  yielded  a  mass  which  was  not  homogeneous, 
which  scratched  glass,  and  which  was  fairly  stable  to  hot  water. 


50  ZIRCONIUM  AND  ITS  COMPOUNDS 

Dilute  hydrochloric  acid  evolved  a  gas,  burning  with  an  almost  color- 
less flame  and  darkening  paper  soaked  in  silver  nitrate  solution.  The 
gas  was  probably  hydrogen  with  some  boron  hydride.  Concentrated 
sulphuric  acid  was  reduced,  evolving  sulphur  dioxide.  When  the  ex- 
periment was  repeated  at  a  higher  temperature  and  a  more  prolonged 
exposure  there  was  formed  a  gray-black  mass  which  was  acted  upon 
by  hydrochloric  acid  only  on  strong  boiling.  The  gas  formed  burned 
with  a  green  flame.  The  mass  was  not  acted  upon  by  sulphuric  acid 
in  the  cold  but  evolved  sulphur  dioxide  on  strong  heating,  which 
would  happen  if  free  carbon  was  present.  Dark  crystals  were  formed 
when  the  mass  was  dissolved  in  melted  copper  and  allowed  to  cool. 
On  analyzing  the  original  mass  it  was  found  to  contain  30.16  p.c. 
of  carbon  and  57.9  p.c.  of  zirconium.  If  the  carbon  is  regarded  as 
admixed  and  the  zirconium  is  calculated  carbon-free,  the  percentage  of 
zirconium  becomes  82.8  and  this  approximates  the  required  percentage 
in  Zr3B4.  The  product  may  be  regarded  as  a  boride  mixed  with 
carbon  or  as  a  borocarbide.  The  experiments  do  not  afford  a  satis- 
factory basis  for  a  decision. 

Zirconium  and  Silicon 

Zirconium  Silicide.  The  preparation  of  the  silicide  by  the  action 
of  silicon  upon  zirconia  was  tried  by  Wedekind  (773)  with  only  par- 
tial success.  When  the  silicon  was  added  in  accordance  with  the 
equation  Zr02  +  Si  =  Si02  +Zr  and  heated  in  an  electric  furnace  a 
dark,  compact  mass  containing  undecomposed  zirconia  was  formed. 
With  an  excess  of  silicon  the  regulus  had  a  metallic  lustre  with  crys- 
talline fracture.  The  broken  surface  showed  silvery  crystals.  These 
crystals  were  very  resistant  to  chemical  action  and  recrystallized  on 
sublimation.  By  mixing  equivalent  weights  of  zirconium  and  silicon 
and  heating  in  vacuum  to  1000°-1200°  a  homogeneous,  gray,  slightly- 
sintered  powder  was  obtained  (791) .  Treating  this  with  warm  caustic 
potash  excess  silicon  was  removed  and  the  silicide  remained. 

Honigschmid  (354)  has  prepared  the  silicide  by  heating  in  a 
Perrot  furnace  a  mixture  of  potassium  fluosilicate  (120  grams),  the 
double  silicate  of  potassium  and  zirconium  (15  grams),  and  aluminum 
(50  grams) .  The  product  was  in  the  form  of  very  brilliant  metallic 
crystals,  which  were  separated  from  aluminum  and  silicon  by  alternate 
treatment  with  hydrochloric  acid  and  a  solution  of  potassium  hydrox- 
ide. The  crystals  still  retained  a  small  amount  of  aluminum — some 


COMPOUNDS  OF  ZIRCONIUM  WITH  THE  ELEMENTS       51 

2  or  3  p.c. — due  doubtless  to  the  formation  of  a  zirconium- aluminum 
alloy.  These  crystals  were  small  and  of  a  clear  iron-gray  color.  They 
formed  rhombic  columns  with  a  prism  of  58°  30'  terminated  by  a 
longitudinal  and  a  transverse  dome.  The  density  was  4.88  and  the 
hardness  approximately  that  of  felspar.  They  remained  unaltered 
in  air.  When  heated  on  platinum  foil  they  were  apparently  unchanged 
but  burned  if  previously  ground  to  a  fine  powder.  When  the  products 
of  combustion  were  treated  with  hydrofluoric  acid  a  brown  residue 
of  amorphous  silicon  was  left.  Heated  in  oxygen  the  crystals  burned 
readily,  forming  silica  and  zirconia.  Fluorine  acted  upon  them  at  a 
slightly  elevated  temperature  with  the  appearance  of  a  flame.  Chlo- 
rine attacked  them  at  a  red  heat,  and  bromine  and  iodine  only  at  a 
high  temperature  but  without  incandescence.  Ordinary  acids  were 
without  action,  except  hydrofluoric  acid,  which  dissolved  them  with 
the  liberation  of  hydrogen.  Solutions  of  alkaline  hydroxide  were 
without  action,  but  when  fused  in  alkali  hydroxides  they  were 
readily  decomposed.  Potassium  bisulphate  showed  no  action. 

By  using  the  thermite  process  Honigschmid  (354,  355)  obtained 
still  better  results.  Pure,  iron-free  sand  (180  grams)  was  mixed  with 
zirconia  (20  grams),  sulphur  (250  grams),  and  pure  aluminum  (200 
grams)  in  a  Hessian  crucible,  covered  with  magnesium  powder,  and 
ignited.  It  was  heated  to  a  white  heat.  The  silicon  and  silicide 
collected  at  the  bottom  of  the  crucible.  After  cooling  this  regulus 
was  separated  from  the  aluminum  sulphide,  broken  up  and  powdered, 
and  then  treated  alternately  with  hydrochloric  acid  and  10  p.c.  potas- 
sium hydroxide  solution  in  a  water  bath.  The  aluminum  and  silicon 
dissolved  and  analysis  showed  much  less  aluminum  retained.  The 
zirconium  silicide  prepared  in  this  way  was  identical  in  properties 
and  composition  with  that  obtained  in  the  Perrot  furnace.  The 
analysis  gave  zirconium  61.8  p.c.  and  silicon  38.2  p.c.  with  a  trace 
of  aluminum.  The  formula,  therefore,  is  ZrSi2.  Wedekind  and 
Pintsch  have  patented  a  process  for  the  commercial  preparation  of 
the  silicide  (791). 

Zirconium  and  Phosphorus 

Zirconium  Phosphide.  Gewecke  (243)  has  prepared  zirconium 
phosphide  by  subliming  zirconium  tetrachloride  in  an  atmosphere  of 
phosphine.  The  reaction  was  carried  out  in  a  piece  of  glass  tubing. 
The  properties  of  the  phosphide  are  closely  parallel  to  those  of  the 
corresponding  titanium  compound  prepared  by  the  same  method. 


52  ZIRCONIUM  AND  ITS  COMPOUNDS 

It  is  a  gray,  glistening  substance  somewhat  like  the  hammer  scales 
from  copper.  The  density  is  4.77  and  it  is  hard  and  brittle.  It  is 
stable  in  air  and  unaffected  by  water.  The  phosphide  resists  ordi- 
nary chemical  reagents  and  conducts  electricity.  The  analysis  showed 
40.18  p.c.  of  phosphorus  and  59.78  p.c.  of  zirconium,  which  agrees  with 
the  percentages  calculated  for  ZrP2. 

Attempts  at  preparing  the  phosphide  by  subliming  the  zirconium 
tetrachloride  over  potassium  phosphide  in  a  stream  of  hydrogen  failed 
to  yield  a  definite  compound  with  constant  proportions.  An  energetic 
reaction  took  place  with  appearance  of  flame,  and  there  was  left  a 
black  mass  out  of  which  potassium  chloride  was  leached  with  water. 
A  graphite-like  substance  was  left  and  this  was  found  to  contain  some 
oxygen. 


Chapter  IV 

Compounds  with  the  Halogens  and  Their  Acids 
Zirconium  and  Fluorine 

Zirconium  Fluoride.  Zirconium  fluoride,  ZrF4,  was  first  pre- 
pared by  Berzelius  (50)  by  dissolving  zirconia  in  hydrofluoric  acid 
until  the  liquid  gave  none  or  only  a  slightly  acid  taste.  Crystals 
were  obtained  by  evaporating  the  solution.  He  stated  that  the  crys- 
talline salt  was  resolved  by  water  into  an  acid  salt  and  a  basic  salt, 
the  latter  being  insoluble.  On  boiling  the  solution  a  partial  precipita- 
tion took  place  and  the  liquid  became  more  acid.  The  hydrolysis  of 
zirconium  salts  in  aqueous  solution  was  thus  distinctly  recognized 
and  the  accompanying  phenomena  recorded  with  the  accustomed  care 
and  accuracy  of  the  great  master.  The  crystalline  substance  reported 
by  Berzelius  as  easily  soluble  was  unquestionably  the  hydrate 
ZrF^SH^O,  as  ZrF4  is  only  slightly  soluble.  According  to  his  view 
of  the  composition  of  the  oxide,  namely,  Zr203,  his  formula  for  the 
fluoride  would  be  given  as  Zr2F3. 

Deville  (181)  prepared  the  fluoride  by  treating  with  hydrogen 
chloride  a  mixture  of  powdered  zircon  and  fluospar  placed  in  a  carbon 
boat  and  enclosed  in  a  carbon  tube.  He  obtained  colorless,  transpar- 
ent crystals,  apparently  belonging  to  the  hexagonal  system  but  im- 
perfectly formed.  The  small  crystals  were  hard  to  measure.  He 
reported  them  as  insoluble  in  water,  not  attacked  by  acids,  and  vola- 
tile at  a  white  heat.  Later,  in  conjunction  with  Caron  (184)  he 
prepared  the  fluoride  by  passing  hydrogen  fluoride  over  powdered 
zircon  heated  to  a  white  heat  in  a  carbon  crucible. 

Marignac  (468)  obtained  the  anhydrous  fluoride  by  heating 
zirconia  with  ammonium  fluoride  or  ammonium-zirconium  fluoride. 
Wolter  (824)  prepared  the  fluoride  by  heating  the  ammonium-zirco- 
nium fluoride,  2NH4F.ZrF4,  driving  off  the  ammonium  fluoride,  and 
purifying  the  zirconium  fluoride  by  sublimation  in  a  stream  of  hydro- 
gen. A  still  better  method  used  by  him  depended  upon  the  double 
decomposition  taking  place  between  zirconium  tetrachloride  and  hy- 

53 


54  ZIRCONIUM  AND  ITS  COMPOUNDS 

drogen  fluoride,  both  carefully  freed  from  water  and  heated  in  a  tube. 
The  analysis  agreed  with  the  formula  ZrF4.  On  subliming  small, 
strongly  refracting  crystals  were  obtained  having  a  density  of  4.43 
at  16°.  The  molecular  weight  at  1200°  was  166.1.  It  was  found  that 
1.388  grams  dissolved  in  100  c.c.  of  water  at  ordinary  temperature 
without  visible  change.  At  50°  hydrolysis  took  place  and  a  white 
precipitate  formed.  The  only  hydrate  obtained  agreed  with  the 
formula  ZrF4.3H20.  With  liquid  ammonia  a  white  pulverulent  com- 
pound was  formed,  having  the  composition  5ZrF4.2NH3.  Gaseous 
ammonia  showed  no  action,  nor  does  this  fluoride  combine  with  pyridin 
and  similar  organic  substances  as  does  the  tetrachloride.  Further- 
more, it  has  much  less  power  of  uniting  with  other  substances  than  its 
isomorphs,  titanium  tetrafluoride  and  stannic  tetrafluoride.  This 
Wolter  attributed  to  the  small  molecular  volume,  37.5,  as  compared 
with  44.3  for  TiF4  and  40.7  for  SnF4,  having  the  same  number  of  atoms 
condensed  in  a  smaller  volume  and  hence  less  freedom  of  motion. 

Zirconium  fluoride,  if  not  too  strongly  ignited,  is  readily  soluble 
in  water.  Crystals  form  on  gently  evaporating  this  solution  acidu- 
lated with  hydrofluoric  acid.  These  crystals,  which  have  a  com- 
position equivalent  to  ZrF4.3H20,  can  be  redissolved  and  recrystal- 
lized  without  change.  On  account  of  this  fact  it  has  been  maintained 
that  the  fluoride  does  not  undergo  hydrolysis,  overlooking  the  early 
experiments  of  Berzelius  which  indicate  clearly  an  hydrolysis. 

Chauvenet  (127)  has  made  a  study  of  the  supposed  compound 
ZrF4.3H20  and  has  come  to  the  conclusion  that  it  is  more  probably 
a  derivative  of  zirconyl  and  has  the  composition  ZrOF2.  H2F2.  2H20, 
a  rearrangement  of  the  same  atoms  in  the  molecule.  It  is  stable  in 
air  and  in  vacuo  but  begins  to  lose  water  at  100°.  At  140°  it  has  the 
composition  ZrOF2.H2F2  but  above  this  temperature  it  loses  hydro- 
fluoric acid  and  becomes  ZrOF2.  This  compound  re'combines  with 
hydrofluoric  acid  when  placed  in  the  cold  acid  and  regains  its  former 
composition.  In  other  words,  the  fluoride  behaves  in  its  action  to- 
wards water  as  the  salts  of  the  other  halogen  acids  do.  The  residue 
left  on  complete  drying  and  calcination  of  the  crystals  is  zirconia, 
though  it  probably  retains  traces  of  fluorine. 

Wedekind  (784)  has  observed  that  in  igniting  zirconia  with  hy- 
drofluoric acid  to  remove  such  silica  as  may  be  present  there  is  a  loss 
of  part  of  the  zirconia.  This  loss  also  occurs  when  a  mixture  of  hydro- 
fluoric acid  and  dilute  sulphuric  acid  is  used  but  may  be  prevented  by 
using  the  sulphuric  acid  in  excess.  In  the  latter  case  all  of  the 


COMPOUNDS  WITH  HALOGENS  55 

fluorine  is  expelled  from  combination  with  the  zirconium.  If  no 
excess  is  present,  ZrF4,  which  is  volatile  at  the  temperature  of  igni- 
tion, may  be  formed. 

Zirconium  Double  Fluorides  or  Fluozirconates.  Conclusive  evi- 
dence is  lacking  to  decide  whether  the  numerous  double  fluorides 
formed  by  zirconium  are  true  fluorzirconates  or  not.  On  the  basis 
of  Chauvenet's  work  already  cited  some  are  zirconyl  fluorides,  and  in 
the  following  description  these  will  be  classified  as  such.  The  fluorides 
and  double  fluorides  of  zirconium  are,  in  general,  isomorphous  with 
those  of  the  analogous  elements,  silicon,  titanium,  and  tin  (stannic), 
and  Gossner  (251,  252)  has  reported  certain  regularities  existing  be- 
tween these  compounds.  For  example,  the  double  fluorides  formed 
with  zinc  fluoride  show  the  following  gradations  in  density. 

»ZnSiF6.6H20    ZnTiF6.6H20    ZnZrF6.6H20    ZnSnF6.6H20 
Sp.  Gr.          2.139  2.106  2.258  2.445 

The  independent  existence  of  a  fluorzirconic  acid,  H2ZrF6,  however, 
has  not  as  yet  been  proved. 

Double  Fluorides  of  Univalent  Elements 

Lithium.  Two  of  these  double  fluorides  have  been  prepared  with 
the  proportions  2  :  1  and  4:1+2/3  H20. 

2LiF.ZrF4  or  Li2ZrF6,  Wells  and  Foote  (809).  When  lithium  fluo- 
ride (0.7-2.0  grams)  is  added  to  zirconium  fluoride  (20  grams)  hex- 
agonal crystals  are  formed,  showing  prism  and  pyramid  and  rarely 
a  basal  plane.  Separate  preparations  were  analyzed,  yielding  results 
in  accord  with  the  above  formula.  This  is  the  normal  lithium  fluo- 
zirconate  Li2ZrF6. 

4LiF.ZrF4.2/3H20  (809).  This  salt  is  formed  when  the  above 
salt  is  recrystallized.  It  also  forms  when  lithium  fluoride  (5-7  grams) 
is  mixed  with  zirconium  fluoride  (20  grams).  It  forms  a  crust  of 
very  small  crystals  which  appear  under  the  microscope  to  be  homo- 
geneous. In  one  preparation  these  crystals  were  mixed  with  the 
2  :  1  variety.  Both  hot  and  cold  solutions  were  used.  On  recrystal- 
lizing  the  small  crystals  were  partially  dissociated  and  some  lithium 
fluoride  crystallized  out.  As  lithium  fluoride  is  very  insoluble  only 
a  comparatively  small  amount  is  dissolved  in  the  solution  of  zirconium 
fluoride.  Hence  there  is  a  tendency  for  the  lithium  fluoride  to  sepa- 
rate and  the  2  :  1  salt  to  form.  Also,  the  observations  reported  and 


56  ZIRCONIUM  AND  ITS  COMPOUNDS 

the  divergences  in  the  analyses  throw  doubt  upon  the  homogeneity 
of  the  substance.  Neglecting  the  water,  it  may  be  written  2LiF .  ZrF4. 
The  zirconium  fluoride  used  in  the  above  experiments  and  in  all  that 
follows  is  of  course  the  hydrated  one,  and  it  must  be  borne  in  mind 
that  doubt  exists  as  to  its  exact  nature,  especially  as  to  whether  or 
not  it  is  a  derivative  of  the  zirconyl  radical.  If  Chauvenet  is  justi- 
fied in  looking  upon  it  as  a  zirconyl  derivative,  the  analysis  would 
tend  to  prove  that  under  the  influence  of  a  stable  fluoride  readjust- 
ment takes  place.  It  must  be  noted  that  some  of  these  salts  are  re- 
ported as  giving  off  hydrofluoric  acid  after  the  water  had  been 
driven  off. 

Sodium.  Two  double  fluorides  are  known,  both  anhydrous,  with 
the  proportions  2:1,  5:2. 

2NaF.ZrF4  (760).  When  from  one  to  two  parts  of  sodium  fluo- 
ride are  added  to  fourteen  parts  of  zirconium  fluoride  a  crust  of  minute 
crystals  of  hexagonal  outline,  which  do  not  recrystallize,  is  formed. 
From  0.5  to  2  p.c.  of  water,  supposed  to  be  mechanically  included,  was 
found  in  the  analysis.  The  fluorine  was  estimated  by  difference. 
This  would  correspond  to  the  normal  fluorzirconate,  Na2ZrF0. 

5NaF.2ZrF4  (468,  809).  This  salt  was  formed  under  widely  vary- 
ing conditions  on  dissolving  together  the  two  fluorides,  also  (468) 
by  double  decomposition  between  sodium  chloride  and  ammonium- 
zirconium  fluoride.  The  crystals  are  described  as  showing  good, 
sharp  forms  but  very  small.  They  appear  distinctly  orthorhombic  in 
habit,  consisting  in  the  main  of  rather  stout  prisms  made  up  of  two 
prismatic  planes  and  terminated  by  a  rather  steep  brachydome.  In 
another  habit,  which  is  rarer,  the  front  pinacoid  is  broadly  developed, 
while  the  prisms  are  very  small.  This  type  also  shows  at  times  a 
pyramid.  The  plane  of  the  optic  axes  lies  in  the  base.  The  optic 
angle  is  large.  The  double  refraction  is  very  low.  In  their  form  the 
crystals  strongly  recall  the  figures  of  chrysolite  (olivine) .  No  loss  of 
weight  was  detected  on  heating,  hence  no  water  was  present.  There 
was  also  no  loss  of  weight  at  red  heat.  The  fluorine  was  estimated  by 
difference.  This  salt  may  be  written  NaF .  2Na2ZrF6. 

Ammonium.  Two  double  fluorides  have  been  reported  2  :  1  and 
3:1,  both  anhydrous. 

2NH4F.ZrF4,  Marignac  (468).  This  salt  was  formed  from  the 
solution  of  the -two  fluorides.  It  exists  in  two  modifications,  Gossner 
(251).  First,  hexagonal  crystals  which  are  formed  on  the  complete 
evaporation  of  the  solution.  These  are  thin,  tabular,  with  very  per- 


COMPOUNDS  WITH  HALOGENS  57 

feet  cleavage,  and  optically  are  weakly  negative.  Second,  rhombic 
bi-pyramidal  crystals,  separate  before  the  hexagonal  in  the  earlier 
stage  of  the  evaporation.  These  are  isomorphous  with  the  correspond- 
ing potassium  salt.  This  compound  is  unchanged  on  heating  to  100°. 
On  stronger  heating  ammonium  fluoride_is  lost  and  ZrF4  is  left  which 
forms  ZrF4.3H2O  on  dissolving  in  water.  This  is  the  normal  fluo- 
zirconate,  (NH4).,ZrF6. 

3NH4F.ZrF4,  Marignac  (468).  This  salt  is  formed  when  a  large 
excess  of  ammonium  fluoride  is  used.  It  forms  regular  octahedra 
and  cubic  octahedra  with  simple  refraction.  When  heated  to  100° 
it  is  unchanged.  The  last  two  ammonium  double  fluorides,  as  well 
as  the  analogous  potassium  salts,  have  the  same  composition  as  those 
of  titanium  but  are  not  isomorphous.  This  salt  may  be  written 
NH4F.(NH4)2ZrF6. 

Potassium.  Three  double  fluorides  are  known — 1  :  1  :  H20,  2:1, 
3  :  1. 

KF.ZrF4.H20,  Marignac  (468).  This  salt  is  formed  only  in  the 
presence  of  a  large  excess  of  zirconium  fluoride.  It  is  decomposed  on 
re-solution  in  water.  This  solution  causes  no  effervescence  on  the 
addition  of  ammonium  carbonate.  The  water  of  crystallization  is  lost 
at  100°.  Heated  beyond  this  temperature  hydrofluoric  acid  escapes. 
The  crystals  are  monoclinic  prisms  or  imperfectly  formed,  short 
prisms,  the  angle  values  showing  a  wide  range.  This  appears  to  be  a 
zirconyl  salt  and  may  be  written  KF.ZROF2.H2F2. 

2KF.ZrF4  (53,  468).  This  is  formed  when  equivalent  parts  of 
potassium  fluoride  and  zirconium  fluoride  are  mixed.  The  crystals 
are  rhombic  pyramidal,  generally  acicular  but  showing  variations. 
This  salt  can  be  heated  up  to  a  red  heat  without  loss  of  weight.  At  a 
red  heat  it  melts  to  a  paste,  giving  off  hydrofluoric  acid,  which  Marig- 
nac attributed  to  the  moisture  in  the  air.  An  instructive  fact  lies  in 
the  rapidly  increasing  solubility  in  water  with  rise  of  temperature. 
One  hundred  c.c.  of  water  at  0°  dissolves  0.781  grams;  at  15°,  1.41 
grams;  at  19°,  1.69  grams;  at  100°,  25.00  grams.  On  cooling  a  boil- 
ing solution  a  mass  of  fine  needlelike  crystals  is  formed.  If  a  less 
concentrated  solution  is  cooled  slowly  the  crystals  obtained  are  not 
in  a  determinable  form. 

The  salt  wras  purified  by  numerous  recrystallizations  and  several 
analyses  made  by  the  usual  method  adopted  by  Marignac  of  adding 
sulphuric  acid,  igniting,  and  weighing  the  zirconia  from  which  the 
potassium  sulphate  had  been  leached.  In  the  filtrate  the  potassium 


58  ZIRCONIUM  AND  ITS  COMPOUNDS 

sulphate  was  determined  but  the  fluorine  was  calculated  from  the 
amount  necessary  to  combine  with  the  potassium  and  zirconium.  The 
formula  may  be  written  K2ZrF6,  the  normal  fluozirconate. 

3KF.ZrF4.  This  salt  is  formed  when  an  excess  of  potassium  fluo- 
ride is  used.  The  crystals  are  in  the  form  of  small,  regular  octahedra 
and  cubic  octahedra,  usually  the  first.  Not  only  do  the  crystal  angles 
agree  with  those  of  the  regular  system  but  they  show  no  double 
refraction.  They  decrepitate  on  heating  to  a  red  heat,  but  if  previ- 
ously pulverized  and  dried  they  suffer  no  loss  of  weight.  The  anal- 
yses of  Marignac  (468)  and  Berzelius  (53)  agree  as  to  their  com- 
position. The  formula  may  be  written  KF.K2ZrF6. 

In  preparing  these  three  compounds  then  the  first  is  formed  in 
the  presence  of  an  excess  of  zirconium  fluoride,  the  last  when  the 
potassium  fluoride  is  in  excess,  and  the  second  when  the  proportions 
lie  between  these  two  extremes. 

Rubidium.  Two  double  fluorides  are  known  in  the  proportions 
2  :  1  and  3  :  1. 

2RbF.ZrF4.  Behrens  (37)  prepared  this  salt  by  adding  rubidium 
chloride  to  a  solution  of  zirconium  sulphate  to  which  ammonium  fluo- 
ride and  free  hydrofluoric  acid  had  been  added.  The  salt  crystallizes 
in  right-angle  prisms.  This  is  the  normal  fluozirconate  Rb2ZrF6. 

3RbF.ZrF4.  This  compound  is  formed  when  the  proportions  in 
the  mixture  are  changed  and  crystallizes  in  strongly  refracting  octa- 
hedra. The  formation  of  these  salts  was  used  by  Behrens  in  his 
microchemical  reactions  for  detecting  rubidium.  The  formula  may 
be  written  RbF.Rb2ZrF6. 

Ccesium.  Three  double  fluorides  are  known,  with  the  proportions 
2:1,  1:1:  H20,  and  2:3:  2H20.  Wells  and  Foote  (808)  have 
prepared  these  salts  by  mixing  the  solutions  of  the  respective  fluorides 
in  varying  proportions  and  adding  more  or  less  of  hydrofluoric  acid 
to  the  sufficiently  concentrated  solution. 

2CsF.ZrF4.  By  the  use  of  an  excess  of  cesium  fluoride  this  salt 
was  formed  even  when  small  amounts  of  zirconium  fluoride  were 
present.  It  crystallizes  in  large  plane  hexagonal  tables,  exhibits  nega- 
tive double  refraction,  and  can  be  recrystallized  without  change.  This 
is  the  normal  fluozirconate  Cs2ZrF6. 

CsF .  ZrF4 .  H2O.  This  salt  is  obtained  by  using  larger  proportions 
of  zirconium  fluoride  than  in  the  preparation  of  the  foregoing  com- 
pound. Monoclinic  crystals  are  formed  which  also  recrystallize  with- 
out change. 


COMPOUNDS  WITH  HALOGENS         59 

2CsF.3ZrF4.2H20.  When  a  large  excess  of  zirconium  fluoride  was 
used  very  small,  difficultly-soluble  crystals  separated  out.  These 
were  too  small  to  determine  crystallographically  but  showed  some 
action  upon  polarized  light.  On  recrystallization  they  were  partially 
changed  into  the  1  :  1  compound.  In  analyzing  these  salts  all 
of  the  constituents  were  determined.  This  salt  may  be  written 
Cs2ZrF6.2(ZrOF2.H2F2). 

Thallium.  Thallium  (809)  forms  four  double  fluorides  or  fluo- 
zirconates  having  the  proportions  1:1,  1:1:  H20,  5:3:  H20,  and 
3:  1. 

T1F .  ZrF4  and  T1F .  ZrF4 .  H20.  When  one  part  of  thallium  fluoride 
is  added  to  a  concentrated  solution  of  three  or  four  parts  of  zirconium 
fluoride  needlelike  crystals  are  formed  containing  one  molecule  of 
water  if  the  solution  is  cooled  before  crystallization.  When  the  solu- 
tion is  evaporated  until  crystallization  begins  and  then  cooled  the 
anhydrous  salt  is  deposited  in  minute  square  plates.  On  recrystalliz- 
ing  the  salt  of  the  5  :  3  types,  having  the  composition  5TlF.3ZrF4.H20, 
is  deposited.  This  salt  crystallizes  in  needles  when  one  to  three  and 
a  half  parts  of  thallium  fluoride  are  added  to  a  solution  of  one  part 
of  zirconium  fluoride.  If  as  much  as  four  parts  of  thallium  fluoride 
are  used  the  same  salt  crystallizes  in  prisms  of  hexagonal  outline, 
which  under  the  microscope  are  seen  to  be  twinned,  and  in  this  respect 
resemble  the  hexagonal-shaped  crystals  of  aragonite.  On  recrystal- 
lization both  give  the  needle-shaped  crystals.  Analyses  of  the  dif- 
ferent forms  show  that  they  have  the  same  composition. 

3TlF.ZrF4.  This  compound  crystallizes  in  brilliant  octahedra 
when  the  solution  of  four  to  twenty  parts  of  thallium  fluoride  are 
added  to  a  solution  of  one  part  of  zirconium  fluoride.  It  recrystallizes 
without  change.  The  following  formulas  may  be  ascribed  to  these 
various  compounds:  (1)  TlF.ZrF4;  (2)  T1F . ZrOF2 . H2F2 ;  (3) 
TlF.2Tl2ZrF6.ZrOF2.H2F2;  (4)  TlF.Tl2ZrF6. 

The  compounds  formed  with  the  univalent  metals  fall  into  several 
types.  First,  there  is  the  normal  fluozirconate,  M2ZrF6.  This  may 
crystallize  with  a  molecule  of  the  alkali  fluoride,  MF.M2ZrF6. 
With  potassium,  cesium,  and  thallium  zirconyl  fluoride  may 
enter  into  the  composition.  Thus  we  have  KF.ZrOF2.H2F2, 
Cs2ZrF6.2(ZrOF2.H2F2),  and  T1F . ZrOF2 . H2F2,  and  lastly  T1F. 
2Tl2ZrF6.ZrOF2.H2F2. 

Double  Fluorides  with  the  Bivalent  Elements.  All  of  these  com- 
pounds crystallize  with  water  of  crystallization. 


60  ZIRCONIUM  AND  ITS  COMPOUNDS 

Copper.  Two  double  fluorides  have  been  prepared  having  the 
proportions  3:2:  16H20,  and  2  :  1  :  12H20. 

3CuF2.2ZrF4.16H2O.  This  salt  was  obtained  by  Marignac  (468) 
on  adding  an  excess  of  zirconium  fluoride  to  a  solution  of  copper 
fluoride  prepared  by  dissolving  copper  carbonate  in  hydrofluoric  acid. 
On  evaporation  there  were  formed  large  crystals  of  the  double  fluo- 
ride accompanied  by  a  pale  blue  crust,  which  was  almost  insoluble 
in  water  and  which  seemed  to  be  zirconium  fluoride  impregnated  with 
the  copper  salt.  The  water  of  crystallization  in  the  large  crystals  is 
lost  on  heating.  These  crystals  form  oblique,  rhombic  prisms  of  a 
beautiful  blue  color. 

2CuF2.ZrF4.12H20.  This  salt  formed  on  adding  copper  fluoride 
to  the  preceding  compound  (468).  It  dissolved  easily  in  cold  water 
without  .change  but  was  dissociated  on  boiling  the  solution,  depositing 
crystals  of  copper  fluoride  and  afterwards  those  of  the  3  :  2  :  16H20 
compound.  The  original  crystals,  of  a  beautiful  blue  color,  are  in 
the  form  of  oblique,  rhombic  prisms  and  are  isomorphous  with  the 
analogous  double  fluorides  of  zinc  and  nickel,  though  the  angles  differ 
slightly. 

Magnesium.  One  double  fluoride  is  known,  with  the  proportion 
1:1:  5H20. 

MgF2.ZrF4.5H20.  This  salt  was  prepared  by  Marignac  (468) 
by  the  action  of  magnesia  upon  an  acid  solution  of  zirconium  fluoride. 
There  is  an  abundant  deposit  of  the  double  fluoride  mixed  with  much 
magnesium  fluoride.  The  double  fluoride  is  not  very  soluble  in  water, 
as  the  two  salts  may  be  separated  by  their  relative  solubilities. 
Crystals  of  the  double  fluoride  can  be  gotten  by  the  gentle  evaporation 
of  their  solution.  These  crystals  are  small  and  generally  form  in 
oblique  rhombohedral  prisms.  Often  crystals  are  found  which  recall 
the  transposed  octahedra  of  the  regular  system  as  seen  in  spinelle. 
The  crystals  are  isomorphous  with  the  corresponding  double  fluoride 
of  manganese.  They  have  also  been  described  by  Groth  (265)  as 
small,  brilliant,  six-sided  monoclinic  tables  with  bent  faces.  The 
salt  is  completely  decomposed  by  prolonged  heating,  leaving  a  residue 
of  zirconia  and  magnesia. 

Calcium,  Strontium,  and  Barium.  These  failed  to  give  well-de- 
fined compounds  (468),  which  may  be  attributed  to  their  insolubility, 
so  that  they  could  not  be  purified  by  crystallization.  When  the  car- 
bonate of  one  of  the  above  elements  was  added  to  an  acid  solution  of 
zirconium  fluoride  the  carbonate  was  decomposed  and  an  insoluble 


COMPOUNDS  WITH  HALOGENS         61 

precipitate,  which  was  a  mixture  of  the  double  fluorides  and  the  zir- 
conium fluoride,  was  formed.  When  barium  chloride  was  added  to  a 
solution  of  potassium-zirconium  fluoride  a  precipitate  formed  imme- 
diately. The  analysis  of  the  precipitate  pointed  to  the  formula 
3BaF2.2ZrF4.2H20,  but  no  decision  could  be  reached  as  to  whether 
it  was  a  compound  or  a  mixture.  Similar  insoluble  precipitates  were 
obtained  in  the  case  of  calcium  and  strontium. 

.  A  similar  insoluble  precipitate  was  obtained  (468)  in  the  case 
of  lead.  Some  of  the  salt,  however,  went  into  solution  and  a  granular, 
somewhat  crystalline  deposit  was  obtained  on  evaporation.  This  was 
decomposed  by  water  and  more  rapidly  by  hydrofluoric  acid,  which 
precipitated  lead  fluoride.  Other  than  this  no  distinct  crystallization 
was  observed.  The  method  of  preparation  used  was  to  add  lead  car- 
bonate to  an  acid  solution  of  zirconium  fluoride  and  evaporate  the 
liquid. 

Zinc.  Two  double  fluorides  have  been  prepared  with  the  propor- 
tions 1:1:6  H20  and  2  :  1  :  12  H20. 

ZnF2.ZrF4.6H20.  Details  are  lacking  as  to  the  formation  of  this 
salt  (468,  265,  252).  Apparently  solutions  containing  equivalent 
parts  of  the  two  fluorides  were  used  in  its  preparation.  It  recrystallizes 
in  long,  hexagonal  prisms  terminating  in  rhombohedra.  It  is  isomor- 
phous  with  the  corresponding  compounds  of  silicon  and  tin  (stannic) 
and  the  analogous  chlorides  of  tin  and  platinum.  It  presents  an  easy 
cleavage  along  the  hexagonal  faces  and  is  very  soluble  in  water.  On 
heating  it  is  decomposed  into  the  oxides  of  zinc  and  zirconium.  The 
zinc  oxide  is  removed  with  difficulty  and  only  imperfectly  by  treat- 
ment with  concentrated  hydrochloric  acid. 

2ZnF2.ZrF4.12H20.    When   an   excess   of   zinc   fluoride   is   used 
this  salt  crystallizes  out.     It  dissolves  easily -in  cold  water  but  is 
partially  decomposed  by  boiling,  depositing  zinc  fluoride.    The  crys-. 
tals  are  monoclinic  prisms  and  are  isomorphous  with  the  correspond- 
ing compound  of  nickel.    The  crystals  are  usually  twinned. 

Cadmium.  Two  double  fluorides  have  been  prepared  with  the 
proportions  1:2:  6H20  and  2:1:  6H20  (468) . 

CdF2.2ZrF4.6H20.  This  salt  crystallizes  from  a  solution  of  the 
two  fluorides  where  the  zirconium  fluoride  is  in  excess.  On  evapora- 
tion there  were  formed  lamellated  crystals  whose  exact  habit  was  not 
determined.  Efforts  at  forming  the  salt  CdF2 .  ZrF4 .  6H20  failed. 

2CdF2.ZrF4.6H20.     Crystals  of  this  salt  are  monoclinic  prisms, 


62  ZIRCONIUM  AND  ITS  COMPOUNDS 

isomorphous  with  the  preceding  salt  and  with  the  corresponding  salt 
of  manganese.  It  can  be  recrystallized  without  change. 

Manganese.  Two  double  fluorides  are  known  with  the  propor- 
tions 1:1:  5H20  and  2  :  1  :  6H20  (468). 

MnF2.ZrF4.5H2O.  This  salt  is  formed  when  manganese  car- 
bonate is  added  to  an  acid  solution  of  zirconium  fluoride.  The  crys- 
tals are  monoclinic  prisms  and  isomorphous  with  the  magnesium  com- 
pound. The  cleavage  is  imperfect  and  the  crystals  are  sometimes 
tabular  and  sometimes  twinned. 

2MnF2 .  ZrF4 .  6H20  (468) .  When  an  excess  of  manganese  carbonate 
and  hydrofluoric  acid  are  added  to  a  solution  of  the  preceding  salt 
short,  thick  prisms  (monoclinic)  of  this  compound  are  formed.  The 
cleavage  is  easy.  These  crystals  dissolve  in  cold  water  without  decom- 
position and  do  not  decompose  on  boiling  the  solution.  If,  however, 
they  are  treated  immediately  with  hot  water  they  decompose  and 
form  an  abundant  deposit  of  manganese  fluoride. 

Nickel.  Two  double  fluorides  are  formed  with  the  proportions 
1:1:  6H20  and  2  :  1  :  12H20  (468). 

NiF2.ZrF4.6H20.  This  salt  is  identical  with  the  fluorsilicate  and 
fluostannate  of  nickel  and  completely  resembles  also  the  correspond- 
ing double  fluoride  of  zinc  except  as  to  color,  which  is  green.  It 
crystallizes  in  regular,  hexagonal  prisms  terminated  by  rhombohedra. 
Cleavage  is  easy  along  the  faces  of  the  prism.  On  calcination  a  mix- 
ture of  the  oxides  of  zirconium  and  nickel  is  left.  The  percentage  of 
fluorine  present  was  not  determined. 

2NiF2 .  ZrF4 . 12H20.  This  salt  is  easily  formed  in  the  presence  of 
an  excess  of  hydrofluoric  acid  and  nickel  fluoride.  It  redissolves  in 
water  without  change  and  is  not  affected  by  boiling,  but  on  standing 
flocculent  nickel  fluoride  is  deposited.  It  crystallizes  with  a  deep 
emerald  green  color  in  oblique,  rhombic  prisms. 

KF.NiF2.2ZrF4.8H20.  This  is  the  only  triple  fluoride  reported 
(468).  These  crystals  are  pale  green  and  in  the  form  of  oblique, 
rhombic  prisms  but  with  a  great  many  modifications.  They  are 
deposited,  practically  quantitatively,  on  mixing  in  equivalent  propor- 
tions solutions  of  the  double  fluorides  of  potassium-zirconium  fluoride 
and  nickel-zirconium  fluoride,  and  are  very  slightly  soluble  in  water. 
If  the  two  solutions  are  in  exactly  equivalent  proportions  the  mother 
liquor  is  entirely  decolorized  and  none  of  the  salts  is  retained  in  solu- 
tion. If  the  solutions  are  hot  and  concentrated  a  mass  of  the  acicular 
crystals  of  the  potassium  compound  is  ordinarily  deposited  and  the 


COMPOUNDS  WITH  HALOGENS  63 

mother  liquor  remains  green,  but  gradually  the  first  crystals  are  redis- 
solved  and  the  triple  compound  is  formed.  The  analysis  is  incom- 
plete as  to  the  fluorine. 

There  seem  to  be  three  types  of  the  double  fluorides  with  the  bival- 
ent elements.  (1)  2MF2.ZrF4.  6  or  12  H20;  (2)  MF2 . ZrF4 . 6H20 ; 
(3)  3MF2.2ZrF4.(H20)n. 

In  view  of  the  presence  of  water  it  is  reasonable  to  assume  that 
all  of  these  are  really  combinations  with  zirconyl  fluoride  and 
should  be  written  as  follows:  (1)  2MF2 . ZrOF2 . H2F2 .  (H20)n; 
(2)  MF2.ZrOF2.H2F2.(H20)n;  (3)  3MF2.  (ZrOF2)2.H2F2.  (H20)n. 
These  compounds  have  not  been  sufficiently  investigated  to  clear  up 
this  question. 

The  experiments  of  Piccini  (550)  with  hydrogen  peroxide  may 
properly  be  given  here.  When  titanium  fluoride  is  treated  with  this  re- 
agent the  reaction  is  a  reversible  one:  TiF4  +  H202  ±+  Ti02F2  +  H2F2. 
A  solution  of  potassium  fluotitanate  (2KF.TiF4.H20)  gives  with  the 
peroxide  on  heating  2KF.Ti02F2;  also  ammonium  fluotitanate  gives 
3NH4F.2Ti02F2.  Neither  zirconium  fluoride  nor  its  double  fluorides 
give  this  reaction. 

Zirconium-Silicon-Fluoride.  Zirconium  hydroxide  dissolves  slight- 
ly in  fluosilicic  acid.  The  filtrate  becomes  cloudy  on  standing  and 
most  of  the  mass  settles  out  as  a  jelly.  After  nearly-completed 
evaporation  of  the  solution  pearly-white  crystals,  which  are  'easily 
soluble  in  water,  are  formed.  The  solution  clouds  on  heating  (49, 
794,  212). 

Zirconium  and  Chlorine 

Zirconium  Tetrachloride  (ZrClJ.  Preparation.  Zirconium  tetra- 
chloride  was  first  prepared  by  Berzelius  (52)  by  the  action  of  chlorine 
upon  metallic  zirconium.  The  reaction  begins  on  gentle  heating  and 
proceeds  with  incandescence.  The  presence  of  water  must  be  care- 
fully guarded  against  in  this  as  in  any  method  for  preparing  this 
salt.  It  was  doubtless  due  to  a  failure  in  this  respect  that  the  product 
obtained  by  him  was  a  white,  non-volatile  mass  only  partially  soluble 
in  water.  The  method  is  in  general  unsatisfactory  because  of  the 
difficulty  of  procuring  pure  zirconium.  For  instance,  the  metal  used 
by  Troost  (714)  undoubtedly  carried  some  aluminum  as  well  as  iron. 
The  tetrachloride  was  prepared  by  Wohler  (820),  Hermann  (319), 
and  Hinzberg  (337)  by  heating  a  mixture  of  zirconia  and  carbon  in  a 


64  ZIRCONIUM  AND  ITS  COMPOUNDS 

stream  of  chlorine.  Instead  of  using  zirconia  Wb'hler  also  used  pow- 
dered zircon.  In  trying  this  method  Melliss  (480)  reported  it  difficult 
to  separate  the  silicon  tetrachloride — an  observation  confirmed  by 
Hornberger  (356).  This  difficulty  might  have  been  overcome,  as 
Troost  and  Hautefeuille  (718)  have  shown  that  silicon  tetrachloride 
undergoes  double  decomposition  when  heated  with  zirconia,  yielding 
silica  and  zirconium  tetrachloride.  Troost  has  also  prepared  this  salt 
by  the  action  of  boron  trichloride  on  zirconia.  Smith  and  Harris 
(663)  found  that  zirconia  reacted  with  phosphorus  pentachloride  when 
heated  in  a  sealed  glass  tube  exhausted  of  air.  The  reaction  did  not 
begin  until  the  temperature  was  raised  above  150°  and  was  complete 
only  after  some  hours  of  heating  at  190°.  There  was  obtained  a 
crystalline  mass  which  was  a  mixture  of  the  tetrachloride  and  phos- 
phorus oxychloride.  Distilled  in  a  stream  of  chlorine  this  gave  the 
nearly-pure  tetrachloride  in  large  crystals  one-half  inch  long.  Wede- 
kind  (785)  obtained  the  chloride  when  the  nitride  was  heated  in  a 
stream  of  chlorine  to  a  dark  red  heat,  and  also  (775)  by  heating  zir- 
conium carbide  in  chlorine.  The  latter  reaction  was  also  noted  by 
Moissan  and  Lengfeld  (501).  Chauvenet  (120)  found  that  carbonyl 
chloride  at  400°  reduced  zirconia,  forming  the  tetrachloride.  When  a 
mixture  of  carbon  monoxide  with  excess  of  chlorine  is  used  (749)  the 
reaction  is  hastened  and  the  initial  temperature  reduced.  Powdered 
zircon*  (25)  is  attacked  by  carbonyl  chloride  at  1250°-1300°.  The 
action  of  a  mixture  of  chlorine  and  sulphur  chloride  was  applied  by 
Bourion  (95)  to  zirconia.  The  reaction  was  stated  to  have  taken 
place  a  little  under  red  heat.  The  product  retains  sulphur  chloride, 
which  produces  a  red  color  that  can  be  removed  by  reheating  in  a 
stream  of  chlorine.  The  action  of  carbon  tetrachloride  on  metallic 
oxides  was  noted  by  Demarcay  (174)  and,  using  zirconia,  he  obtained 
the  tetrachloride  at  the  temperature  of  boiling  sulphur.  Camboulives 
(115)  repeated  the  experiment,  noting  400°  as  the  temperature  at 
which  the  zirconia  was  attacked.  Meyer  and  Wilkens  (491)  failed  to 
observe  -any  reaction  with  zirconia  at  the  temperature  of  the  Glaser 
furnace.  The  gases  formed  in  the  reaction  were  examined  and  found 
to  be  carbon  monoxide,  carbon  dioxide,  carbonyl  chloride,  and  chlorine 
when  using  alumina  as  the  metallic  oxide.  The  carbon  tetrachloride 
was  introduced  by  bubbling  an  inert  gas  through  it.  This  probably 
accounts  for  the  failure  to  get  a  reaction  with  zirconia,  which  is  more 
difficultly  attacked.  Lely  and  Hamburger  (440)  used  carbon  tetra- 
chloride and  chlorine  and  reported  the  reaction  as  taking  place  at  800°. 


•  COMPOUNDS  WITH  HALOGENS  65 

Venable  and  Bell  (744)  found  this  method  the  most  convenient  one 
for  the  preparation  of  the  tetrachloride,  passing  the  stream  of  chlorine 
through  a  vessel  containing  carbon  tetrachloride  and,  thus  saturated 
with  its  vapor,  over  the  zirconia  in  a  glass  tube  heated  by  an  electric 
sleeve.  The  reaction  began  at  about  300°  and  was  abundant  at 
550°-600°.  The  yield  is  quantitative.  They  also  tried  the  method, 
which  had  been  used  by  Chauvenet  and  others,  dependent  upon  the 
dissociation  of  dried  zirconyl  chloride.  This  drying  is  best  done 
under  a  stream  of  hydrochloric  acid.  The  dissociation,  2ZrOCl2  =• 
Zr02  +  ZrCl4,  begins  at  about  300°  (according  to  Lely  and  Ham- 
burger, 600°).  The  yield  in  several  experiments  was  less  than  10  p.c. 
of  the  theoretical,  due  doubtless  to  failure  in  meeting  the  exact  con- 
ditions of  previous  dehydration  and  subsequent  dissociation. 

Properties.  Zirconium  tetrachloride  is  a  white,  crystalline  sub- 
stance, easily  volatilized  at  about  300°,  subliming  in  clear,  bright 
crystals  of  fair  size  if  care  is  observed  in  volatilizing  and  cooling.  The 
vapor  density  has  been  determined  at  440°-450°  by  Hermann  (319). 
and  Deville  and  Troost  (185)  with  only  partially  satisfactory  results. 
No  modern  determinations  seem  to  have  been  recorded.  On  exposure 
to  air  abundant  fumes  of  hydrochloric  acid  are  given  off.  The  reac- 
tion with  water  is  most  energetic,  evolving  much  heat  and  forming 
zirconyl  chloride.  Covered  with  anhydrous  hydrofluoric  acid  and 
heated  zirconium  tetrafluoride  is  formed,  Wolter  (824).  The  density 
of  the  solid  as  determined  with  carbon  tetrachloride  at  room  tem- 
perature (744)  is  2.8.  It  is  reported  as  dissolving  in  absolute  alcohol 
with  hissing  (356,  337),  but  neither  an  alcoholate  nor  hydrate  could 
be  obtained  from  the  solution  (609).  On  boiling  this  solution  ethyl 
chloride  was  liberated  (356).  If  the  alcoholic  solution  is  saturated 
with  hydrogen  chloride  organic  salts  of  a  zirconium  tetrachloride- 
hydrogen  chloride  of  the  type  M2H2ZrCl6  can  be  formed  where  M 
is  pyridin,  chinolin,  etc.  The  tetrachloride  is  also  soluble  in  ether. 
According  to  Rosenheim  and  Hertzmann  (611),  a  molecular  com- 
pound was  formed  with  the  ether  but  this  was  not  obtained  pure.  In 
ethereal  solution  it  can  form  addition  compounds  with  ammonia  and 
various  organic  bases.  Many  compounds  are  also  formed  with  other 
organic  substances. 

Addition  compounds.  With  sodium  chloride — 2NaCl.ZrCl4. 

Paykull  (536)  prepared  this  compound  by  heating  sodium  chloride 
to  fusion  in  contact  with  volatilized  zirconium  tetrachloride. 


66  ZIRCONIUM  AND  ITS  COMPOUNDS 

With  potassium  chloride.  By  the  same  method  Weibull  (794) 
prepared  a  similar  compound  with  potassium  chloride. 

With  ammonia— ZFCl4.8NH3.—Stahler  and  Denk  (674)  found 
that  this  compound  was  formed  when  ammonia  was  passed  for  about 
twelve  hours  over  zirconium  tetrachloride  at  16°  until  the  weight  was 
constant.  Heat  is  evolved  in  the  reaction  and  a  white  powder  is  left. 
On  heating  this  ammonia  was  first  lost  and  then  ammonium  chloride 
driven  off.  The  powder  is  very  hygroscopic  when  exposed  to  air  and 
loses  ammonia.  With  water  it  reacts  strongly,  ammonium  chloride 
being  formed  and  zirconium  hydroxide  precipitated.  Matthews  (471) 
obtained  ZrCl4.2NH3  by  the  same  method,  passing  the  stream  of 
ammonia  only  two  hours.  When  ammonia  is  passed  over  the  heated 
tetrachloride  (673)  a  white,  unstable  compound,  ZrCl4.3NH3,  is 
formed  below  232°.  Matthews  (471)  has  reported  this  method  as 
giving  ZrCl4.NH3  and,  on  further  heating,  as  losing  ammonium  chlo- 
ride and  leaving  the  nitride  as  final  product.  He  also  prepared  the 
compound  ZrCl4.8NH3  by  passing  dry  ammonia  into  a  solution  of 
the  tetrachloride  in  absolute  ether.  Heat  was  liberated  as  a  white, 
flocculent  precipitate  was  formed.  On  drying  this  salt  was  found 
stable  in  the  air.  Paykull  (536)  also  prepared  ZrCl4.4NH3. 

NOC1,  N02,  S2C12,  PC13,  PC15,  C2N2,  and  the  nitriles  give  no 
reaction  with  zirconium  tetrachloride  (471,  663).  Compounds  have 
been  formed  (471)  by  passing  vapors  of  organic  amines  into  an  ethe- 
real solution  of  the  tetrachloride. 

By  saturating  absolute  alcohol  with  hydrogen  chloride,  adding  an 
excess  of  zirconium  hydroxide,  and  heating  with  a  reflux  condenser 
a  solution  was  obtained  by  Rosenheim  and  Frank  (609)  which  was 
filtered  cold  and  again  saturated  with  hydrogen  chloride.  This 
formed  well-crystallized  salts  on  the  addition  of  concentrated  solu- 
tions of  pyridin  chlorhydrate  and  quinolinchlorhydrate,  with  the  com- 
position (C5H5N)2H2ZrCl6  and  (C9H7N)2H2ZrCl6,  respectively.  This 
solution  in  absolute  alcohol,  saturated  with  hydrogen  chloride,  there- 
fore contains  zirconium  tetrachloride,  but  no  hydrate  of  this  was 
formed  (such  as  had  been  reported  by  earlier  investigators  working 
under  different  conditions)  nor  could  any  alcoholates  be  detected. 

Organic  amines  added  to  aqueous  solutions  give  the  same  pre- 
cipitate as  ammonia  (752,  753). 

Zirconyl  Chloride  (ZrOCl2).  This  compound  is  formed  by  hydrol- 
ysis when  the  tetrachloride  is  exposed  to  moist  air  or  dissolved  in 
water.  On  crystallizing  it  combines  with  water  of  crystallization. 


COMPOUNDS  WITH  HALOGENS  67 

It  is  also  formed  by  dissolving  the  hydroxide  in  hydrochloric  acid. 
From  such  a  solution  colorless,  needlelike  crystals  having  a  somewhat 
bitter,  astringent  taste  are  obtained.  If  the  solution  is  made  strongly 
acid  the  crystallization  is  nearly  quantitative,  the  hydrated  zirconyl 
chloride  being  only  slightly  soluble  in  concentrated  hydrochloric  acid. 
The  addition  of  water  precipitates  this  chloride  from  an  acid  solution 
and  concentrated  hydrochloric  acid  precipitates  it  from  an  aqueous 
solution.  These  precipitates  are  gradually  redissolved  on  standing, 
this  re-solution  depending  upon  the  relative  proportions  of  the  pre- 
cipitant. 

These  crystals  have  the  composition  ZrOCl2 .  8H20  and  form  tetrag- 
onal prisms  with  distinct  cleavage  (265,  304).  They  are  stable  in 
air  and  effloresce  over  a  dehydrating  agent,  losing  hydrochloric  acid 
at  the  same  time.  They  are  easily  soluble  in  water  and  no  precipi- 
tate is  formed  on  heating  the  solution  but  hydrochloric  acid  is  liber- 
ated. They  are  also  soluble  in  ether  and  alcohol.  Dilute  hydro- 
chloric acid  dissolves  them  but  the  concentrated  acid  has  little  solvent 
action. 

The  existence  of  several  hydrates  of  zirconyl  chloride  has  been 
reported  by  different  investigators.  Some  of  these  are  manifestly 
erroneous.  The  following  appear  in  the  literature.  ZrOCl2.9H20 
(319);  ZrOCl2.8H20  (536);  ZrOCl2 . 6 . 5H20  (537);  ZrOCl2.6H20 
(742);  ZrOCl2.5.5H20  (434);  ZrOCl2.4.5H20  (479);  ZrOCl2.4H20 
(434);  ZrOCl2.3.5H20  (122);  ZrOCl2.3H2O  (736);  ZrOCl2.2H20 
(434,  122).  Some  of  these  variations  may  be  accounted  for  by  the 
conditions  under  which  the  investigations  were  carried  out,  such  as 
imperfect  drying,  range  of  temperature  with  possible  partial  hydrol- 
ysis, loss  of  hydrochloric  acid,  and  whether  dried  in  air  or  in  a  stream 
of  hydrogen  chloride.  The  hydrates  with  9  and  with  6.5  molecules 
of  water  may  be  definitely  excluded,  and  quite  probably  those  with 
5.5  and  4.5  molecules.  Chauvenet  (122)  from  thermochemical  data 
has  limited  the  number  to  those  with  8,  6,  3.5,  and  2  molecules  of 
water. 

These  hydrates  have  been  obtained  as  follows: 

Normally,  the  zirconyl  chloride  crystallizes  with  8  molecules  of 
water  and  has  the  composition  ZrOCl2.8H20.  Such  crystals  are 
formed  whenever  the  solution  is  evaporated  at  ordinary  temperature. 
They  are  also  formed  on  the  addition  of  concentrated  hydrochloric 
acid  to  the  aqueous  solution.  If  the  solution  is  concentrated  a  curdy 
precipitate  is  formed.  The  crystals  are  soluble  in  boiling  hydro- 


68 


ZIRCONIUM  AND  ITS  COMPOUNDS 


chloric  acid  but  are  deposited  again  on  cooling,  and  this  recrystalliza- 
tion  from  boiling  hydrochloric  acid  furnishes  a  method  for  the  puri- 
fication of  the  chloride.  The  crystals  of  this  hydrate  may  be  dried 
in  air  without  loss  of  hydrochloric  acid.  In  dry  air  they  effloresce 
and  the  loss  of  water  ceases  when,  they  reach  a  weight  corresponding 
to  ZrOCl2.6H20.  If  the  dehydration  is  carried  further  in  a  stream 
of  dry  air  at  50°  the  limit  ZrOCl2.3.5H20  is  reached  (122).  If 
heated  in  a  stream  of  hydrogen  chloride  at  a  temperature  not  exceed- 
ing 125°  the  composition  is  ZrOCl2.3H20  (736).  If  the  temperature 
is  raised  to  150°  ZrOCl2.2H20  is  left  (122).  The  last  of  the  water 
of  hydration  is  lost  at  180°-210°  (736). 

Hydrolysis  of  the  Chlorides.  As  has  been  stated,  zirconium  tetra- 
chloride  when  brought  in  contact  with  water  is  quickly  hydrolyzed 
to  zirconyl  chloride.  This  hydrolysis  progresses  further.  Aqueous 
solutions  of  zirconyl  chloride  always  have  an  acid  reaction  and  on 
standing  the  salt  present  undergoes  progressive  hydrolysis  even  at 
ordinary  temperature.  This  hydrolysis  is,  of  course,  affected  by  such 
conditions  as  temperature  and  concentration.  Ruer  (619)  has  meas- 
ured this  hydrolysis  in  a  one-fourth  normal  solution  of  ZrOCl2.8H20 
at  18°,  according  to  the  time  elapsed  after  solution,  by  the  specific 
conductivity. 


After    5  minutes 
1      10 
'        1  hour 
'        3.5 

5 

6 

'  24 
'  48 
'  72 

1    168.. 
'      boiling 

72  hours  later 


-5  -1  -1 
1469  X  10  ohm  c.c. 
1556 
1867 
1965 
1980 
1989 
2024 
2071 
2104 
2107 
2777 
2722 


This  increase  in  conductivity  is  due  of  course  to  the  hydrochloric 
acid  liberated.  The  change  is  rapid  in  the  first  sixty  minutes  at  an 
average  rate  of  67  X  10'5  ohm"1  c.c.'1  per  minute.  For  the  next  168 
hours  it  is  nearly  stationary,  averaging  0.014  X  10"5  ohm'1  c.c."1  per 
minute,  indicating  the  formation  of  a  more  stable  basic  chloride 
which  breaks  down  under  the  influence  of  heat  with  a  rapid  increase 
of  more  than  30  p.c.  in  conductivity.  At  this  point  the  liberation  of 
hydrochloric  acid  seems  to  come  to  an  end  and  a  slow  reversal  is 
shown,  doubtless  due  to  the  gradual  escape  of  the  freed  acid  or  partial 


COMPOUNDS  WITH  HALOGENS         69 

recombination.  When  ionized  in  solution  the  zirconyl  radical  forms 
the  cation.  In  a  2  p.c.  solution  of  zirconyl  chloride  in  half-normal 
hydrochloric  acid  (time  14  hours,  current  0.05  amp.)  0.0280  grams  of 
Zr02  were  found  in  the  cathode  arm  and  0.0005  grams  in  the  anode. 

In  the  course  of  the  hydrolysis  and  under  varying  conditions  of 
temperature  and  concentration  certain  definite  basic  zirconyl  chlo- 
rides are  formed.  The  first  of  these  is  Zr203Cl2  (on  water-free  basis) 
as  described  by  Endemann  (209).  It  may  be  precipitated  from  an 
alcoholic  solution  of  zirconyl  chloride  by  the  addition  of  ether  and, 
as  Chauvenet  (122)  has  shown,  retains  three  molecules  of  water. 
More  properly  then  the  formula  may  be  written  ZrO(OH)2ZrOCl2. 
It  can  be  prepared  (122)  in  the  water-free  condition  by  heating  the 
hydrate  ZrOCl2.2H,0  to  230°  under  hydrogen  chloride.  This  basic 
chloride  is  soluble  in  water  and  may  be  transformed  into  ZrOCl2  by 
adding  concentrated  hydrochloric  acid  and  warming.  At  300°  the 
water-free  ZrOCl2  and  Zr203Cl2  dissociate  into  ZrCl4  and  Zr02.  Ende- 
mann reported  also  a  basic  zirconyl  chloride  with  the  composition 
Zr304Cl2,  the  existence  of  which  has  not  been  confirmed.  When  zir- 
conyl chloride  or  the  basic  chlorides  are  heated  to  a  high  temperature 
a  small  portion  of  the  chlorine  is  retained  even  after  prolonged  heating 
at  1000°.  The  hydrolysis  of  zirconyl  chloride  at  0°  and  20°  has  been 
measured  by  Venable  and  Jackson  (749) . 

In  dialyzing  zirconyl  chloride,  Ruer  (618)  found  that  a  hydrosol 
with  a  lower  ratio  than  Zr02  :  Cl  : :  0.2958  :  0.0060  was  not  obtainable. 
This  chlorine  could  not  be  separated  by  silver  nitrate  except  after 
treatment  with  nitric  acid.  A  gel  of  zirconyl  hydroxide  separated  in 
the  dialysis.  The  hydrosol  contained  colloidal  hydroxide  which  could 
be  freed  from  the  small  amount  of  chlorine  by  adding  first  silver 
nitrate  in  the  proper  amount,  then  nitric  acid,  and  warming  or  agitat- 
ing. By  evaporating  a  dilute  solution  of  zirconyl  chloride  to  a  very 
small  volume,  diluting  and  evaporating  again  three  or  four  times,  most 
of  the  hydrochloric  acid  liberated  on  hydrolysis  was  driven  off,  Ruer 
(619).  The  liquid  became  opalescent  and  finally  milky.  The  final 
evaporation  left  about  15  c.c.  A  very  finely  divided  precipitate  set- 
tled out,  leaving  a  liquid  in  which  very  little  zirconium  could  be 
detected.  Washing  with  water  caused  the  liquid  to  become  milky  once 
more.  The  precipitate  was  centrifuged.  Concentrated  hydrochloric 
acid  was  added  and  the  centrifuging  repeated.  Water  was  added,  then 
hydrochloric  acid,  and  the  mixture  centrifuged,  and  these  operations 
repeated.  The  yield  of  precipitate  was  almost  quantitative.  It  was 


70  ZIRCONIUM  AND  ITS  COMPOUNDS 

dried  in  vacuo  over  sulphuric  acid  and  over  potassium  hydroxide  and 
yielded  a  loose  white  powder.  Four  preparations  showed  this  to  be 
of  practically  constant  composition.  No  formula  for  the  substance 
is  given  by  Ruer,  but  on  calculation  from  his  analyses  its  composition 
corresponds  closely  with  9ZrO(OH)2.ZrOCl2.  aq.  It  was  only  par- 
tially dried  when  heated  to  130°,  losing  almost  no  hydrochloric  acid, 
showing  that  part  of  the  water  is  very  firmly  held.  This  compound 
Ruer  (619)  called  metazirconic  chloride.  It  is  really  a  highly  hydro- 
lyzed  basic  chloride  and  on  the  water-free  basis  might  be  represented 
by  the  formula  Zr10019Cl2.  The  formula  given  above  goes  to  show 
that  out  of  10  molecules  of  zirconyl  chloride  9  had  undergone  hydrol- 
ysis. This  substance  before  drying  is  soluble  in  water.  On  dialyzing 
this  solution  a  colloidal  solution  containing  less  than  1  p.c.  of  chlorine 
is  obtained;  hence  it  is  a  solution  of  nearly  pure  zirconyl  hydroxide 
or  metazirconic  acid.  It  is  difficult  to  transform  this  basic  chloride 
into  zirconyl  chloride  by  the  action  of  hydrochloric  acid  after  once 
removing  the  excess  of  water.  After  boiling  five  grams  with  a  half- 
liter  of  concentrated  hydrochloric  acid  for  three  hours  only  20  p.c. 
had  been  changed.  For  complete  change  it  was  necessary  to  heat  it 
with  one  kilo  for  thirty  hours. 

By  dissolving  zirconium  hydroxide  in  hydrochloric  acid,  concen- 
trating, and  crystallizing  it  has  been  claimed  (247)  that  a  crystalline 
mixture  of  ZrOCl2.8H2O  and  Zr508Cl2.22H20  is  obtained.  It  is 
stated  that  this  new  basic  chloride  can  be  separated  from  hydrochloric 
acid  by  recrystallization.  The  existence  of  this  salt  with  its  peculiar 
behavior  lacks  confirmation.  The  existence  of  a  basic  chloride 
Zr402Cl6,  which  Troost  and  Hautefeuille  (716)  reported  as  formed 
when  ZrCl4  was  heated  in  a  stream  of  oxygen,  has  been  shown  by 
Chauvenet  (122)  to  be  an  error.  If  the  oxygen  is  not  thoroughly 
dried  a  small  amount  of  the  tetrachloride  is  hydrolyzed  to  zirconyl 
chloride,  which  breaks  up  on  heating  into  zirconia  and  chlorine.  This 
zirconia  in  small  amounts  may  be  entrained  in  the  vapor  of  the  tetra- 
chloride. In  larger  amounts  its  presence  is  shown  by  its  insolubility. 

Double  compounds.  Nilson  (518)  on  mixing  a  solution  of 
ZrOCl2.8H20  with  chloroplatinic  acid,  H2PtCl6,  obtained  crystals  in 
the  form  of  small,  clear,  yellow  prisms.  They  were  fairly  stable  in 
the  air.  The  melting  point  was  100°.  One-half  the  water  was  lost 
at  this  temperature,  giving  a  shellac-like  mass.  The  composition  is 
represented  by  the  formula  ZrOCl2.PtCl4.12H20.  Also  a  compound 


COMPOUNDS  WITH  HALOGENS         71 

was   obtained  with   platinous   chloride   which   had  the  composition 
ZrOCl2.PtCl2.8H20. 

Compounds  with  Chl-oric  Acid.  The  normal  chlorate  (ZrC103)4 
has  probably  not  been  prepared,  though  Weibull  (794)  stated  that  he 
had  prepared  it  by  double  decomposition  according  to  the  equation 
Zr(S04)2  +  2Ba(C103)2  =  Zr(ClO3)4+2BaS04.  No  details  or 
analyses  are  given.  This  is  manifestly  erroneous,  since  both  zirco- 
nium sulphate  and  chlorate  are  hydrolyzed  in  aqueous  solution.  A 
basic  zirconyl  chlorate  has  been  prepared  by  Venable  and  Smithey 
(751)  by  adding  a  solution  of  potassium  chlorate  to  a  cold  solution 
of  zirconium  perchlorate,  crystallizing  out  the  potassium  perchlorate, 
and  allowing  the  basic  zirconyl  chlorate  to  crystallize  over  phosphorus 
pentoxide.  It  forms  fairly  large,  distinct  crystals  which  were  very 
deliquescent  and  could  not  be  dried  over  sulphuric  acid  or  calcium 
chloride.  They  were  soluble  in  alcohol  but  not  in  ether.  These  crys- 
tals oxidize  organic  matter  and  are  slightly  yellowish  in  color  from 
partial  decomposition,  chloric  acid  being  liberated  with  the  formation 
of  chlorine  dioxide.  The  composition  of  the  crystals  agrees  with  the 
formula  ZrO(OH)2.3ZrO(C103)2. 

Compounds  with  Perchloric  Acid.  The  normal  zirconyl  perchlo- 
rate has  not  been  prepared.  An  acid  perchlorate  or  zirconyl  perchloric 
acid  has,  however,  been  prepared  by  Venable  and  Smithey  (751)  by 
dissolving  the  hydroxide  in  perchloric  acid  at  ordinary  temperature 
in  the  presence  of  an  excess  of  hydroxide.  It  forms  large  crystals  of 
the  triclinic  system,  which  explode  when  sharply  heated.  The  anal- 
yses correspond  with  the  formula  4ZrO(C104)2.C104H. 

When  the  perchloric  acid  was  saturated  with  zirconyl  hydroxide 
by  heating  on  a  water  bath  with  excess  of  hydroxide  radiating  clusters 
of  crystals  were  formed  from  which  single  crystals  could  not  well 
be  separated.  These  were  very  deliquescent,  soluble  in  alcohol,  ether, 
benzene,  chloroform,  and  carbon  tetrachloride,  but  no  crystals  were 
obtained  from  these  solutions.  A  small  portion,  heated  rapidly  on 
platinum,  exploded  with  a  sharp  report.  Decomposition  was  evident 
at  100°.  Slowly  heated  they  intumesced  and  finally  left  a  white 
powder  of  zirconia.  Several  preparations  were  made.  The  analyses 
correspond  with  the  formula  ZrO(OH)2.9ZrO(C10J2.  One  molecule 
of  the  zirconyl  perchloric  acid  therefore  seems  to  dissolve  one  mole- 
cule of  zirconyl  hydroxide,  giving  a  compound  in  which  the  ratio  of 
zirconyl  hydroxide  to  zirconyl  perchlorate  is  1  :  9.  On  recrystallizing 


72  ZIRCONIUM  AND  ITS  COMPOUNDS 

this  product  it  is  dissociated  and  the  original  zirconyl  perchloric  acid 
formed  (751). 

Zirconium  and  Bromine 

Zirconium  Tetrabromide  (ZrBr4).  This  has  been  prepared  (480) 
by  passing  carbon  dioxide  saturated  with  bromine  vapors  over  a  mix- 
ture of  zirconia  and  charcoal  heated  to  a  bright  red  "heat.  It  forms 
a  white,  crystalline  powder  which  can  be  volatilized  without  decom- 
position. It  is  not  reduced  by  hydrogen  at  a  white  heat  but  is  decom- 
posed by  moist  air  and  reacts  energetically  with  water,  yielding  a 
solution  of  zirconyl  bromide.  It  has  also  been  prepared  by  passing 
bromine  vapors  over  heated  zirconium  (22)  or  the  carbide  (674). 
Here,  also,  a  stream  of  "carbon  dioxide  may  be  used  as  the  carrier. 
It  is  very  hygroscopic,  giving  off  hydrobromic  acid.  It  is  soluble 
in  alcohol  or  ether. 

The  tetrabromide  forms  compounds  with  ammonia  in  a  manner 
similar  to  the  tetrachloride.  Thus,  when  saturated  with  ammonia 
passing  over  it  at  16°  it.  forms  the  compound  ZrBr4.10NH3  (674). 
This  is  a  very  hygroscopic  white  powder,  giving  off  ammonia.  If 
warmed  (472)  it  forms  a  somewhat  more  stable  compound  ZrBr4.4NH3, 
which  on  heating  gives  the  nitride  and  by  further  heating  in  hydrogen 
yields  the  metal.  With  ethylamine  the  compound  ZrBr4.4C2H5NH2 
is  formed;  with  anilin,  ZrBr4.4C6H5NH2;  and  with  pyridin 
ZrBr4.2C5H5N,  showing  the  same  power  of  forming  addition  com- 
pounds with  organic  bases  that  the  tetrachloride  has.  Rosenheim 
and  Frank  (609),  by  the  addition  of  pyridin  and  chinolin  to  a  solu- 
tion of  hydrogen  bromide  in  alcohol  saturated  with  zirconium  hydrox- 
ide, obtained  the  compounds  (C5H5N)  2H2ZrBr6  and  (C9H7N)2H2ZrBr6. 

Zirconyl  Bromide  (ZrOBr2).  This  can  be  prepared  by  dissolving 
zirconyl  hydroxide  in  hydrobromic  acid  and  allowing  the  solution  to 
evaporate  to  crystallization.  It  can  also  be  prepared  by  the  hydrol- 
ysis of  the  tetrabromide  in  aqueous  solution  or  by  dissolving  the 
hydroxide  in  a  saturated  solution  of  hydrogen  bromide  in  absolute 
alcohol.  The  crystals  are  granular  (44)  or  fine,  brilliant,  needlelike 
(742),  optically  uniaxial,  tetragonal,  and  isomorphous  with  the  cor- 
responding zirconyl  chloride.  The  formula  usually  assigned  them  is 
ZrOBr2.8H20,  but  it  is  difficult  to  remove  the  surplus  water  without 
decomposition,  so  as  much  as  13  and  14  molecules  of  water  of  crys- 
tallization have  been  reported.  The  crystals  readily  lose  hydrobromic 
acid  in  a  current  of  dry  air  or  when  placed  over  a  dehydrating  agent. 


COMPOUNDS  WITH  HALOGENS         73 

They  are  more  hygroscopic  than  the  zirconyl  chloride  crystals,  decom- 
posing on  exposure  to  moist  air.  These  crystals  are  soluble  in  hot, 
concentrated  hydrobromic  acid,  crystallizing  out  again  on  cooling. 
Dried  at  100°-120°  in  a  rapid  stream  of  hydrogen  bromide  a  hard, 
crystalline  solid  (742)  which  is  readily  soluble  in  water  is  obtained. 
This  has  the  composition  ZrOBr2.4H20. 

Basic  Zirconyl  Bromide  ZrO(OH)2.ZrOBr2.3H20  (or  4H20). 
This  basic  salt  (742)  was  obtained  by  the  prolonged  boiling  of  a  satu- 
rated solution  of  the  hydroxide  in  concentrated  hydrobromic  acid  and 
subsequent  evaporation  of  the  solution  (deeply  colored  with 
bromine)  on  a  water  bath.  White  crystals  with  the  composition 
ZrO(OH)2.ZrOBr2.4H20  separated  out.  Gelatinous  zirconyl  hydrox- 
ide was  also  distributed  through  the  solution.  Another  crop  of  smaller 
needlelike  crystals  was  obtained  on  further  evaporation  of  the  solution. 
These  had  the  composition  ZrO(OH)2.ZrOBr2.3H20.  The  gelatinous 
hydroxide,  retaining  some  bromine,  could  be  separated  as  a  hydrogel 
by  dialysis,  the  basic  zirconyl  bromide  going  into  solution.  A  basic 
zirconyl  bromide  of  a  similar  composition  was  obtained  also  by 
Weibull  (795). 

Zirconium  and  Iodine 

Zirconium  Tetraiodide  (ZrlJ.  Attempts  to  prepare  this  salt  by 
the  action  of  iodine  upon  a  mixture  of  zirconia  and  carbon  raised  to 
a  high  temperature  have  failed  (480).  Nor  was  it  formed  when 
vapors  of  the  tetrabromide  were  passed  over  heated  potassium  iodide 
(480.)  Furthermore,  iodine  seems  to  have  slight  direct  action  upon 
metallic  zirconium  (22,  480).  Hydrogen  iodide,  however,  acts  upon 
the  metal  at  340°  or  upon  the  carbide  at  490°.  The  reaction  is  ener- 
getic and  a  rust-brown  sublimate  is  formed  intermixed  with  iodine 
crystals.  No  white  sublimate  was  observed  by  Stahler  and  Denk 
(673).  The  excess  of  iodine  was  removed  by  washing  with  benzene, 
leaving  a  red-brown  residue  which  appeared  as  a  crystalline  powder 
when  examined  under  the  microscope.  This  fumed  in  the  air  and 
dissolved  in  water  with  energetic  reaction.  It  also  reacted  energeti- 
cally with  alcohol,  giving  zirconyl  hydroxide  and  ethyl  iodide.  It  is 
slightly  soluble  in  benzene  or  carbon  disulphide  and  more  readily 
soluble  in  ether,  giving  a  yellow  addition  product.  It  is  strongly 
hydrolyzed  by  water  and  decomposed  by  strong  acids  (673).  Older 
statements  that  are  apparently  irreconcilable  with  these  occur  in  the 
literature  (176). 


74  ZIRCONIUM  AND  ITS  COMPOUNDS 

The  possible  existence  of  a  periodide,  ZrI4.I2,  has  been  based  (674) 
upon  the  fairly  constant  proportions  observed  in  the  product  obtained 
in  the  preparation  of  the  tetraiodide  before  the  treatment  with  ben- 
zene. On  subliming  this  product  at  a  temperature  over  300°  a  heavy, 
dark-brown  vapor,  which  condensed  to  a  red-brown  powder,  was 
formed. 

Addition  compounds.  Addition  compounds  are  formed  by  the 
tetraiodide  with  ammonia.  When  a  stream  of  dry  ammonia  is  passed 
(674)  over  crystals  of  the  tetraiodide  at  a  temperature  not  exceeding 
22°  a  constant  weight  is  reached  at  which  the  composition  corresponds 
to  the  formula  ZrI4.8NH3.  This  substance,  according  to  Stabler 
and  Denk,  may  be  regarded  possibly  as  a  double  compound  of  the 
amid  and  ammonium  iodide,  and  on  that  basis  would  be  ascribed  the 
formula  Zr(NH2)4.4NH4I.  Liquid  ammonia  largely  dissolves  and 
separates  the  ammonium  iodide.  Against  this  view,  however,  may 
be  considered  the  gradual  loss  of  ammonia  on  raising  the  temperature. 
At  100°  the  composition  is  ZrI4.7NH3;  at  150°  it  is  ZrI4.6NH3; 
and  up  to  200°  it  is  ZrI4.4NH3.  At  this  temperature  decomposition 
begins  to  take  place  and  ammonium  iodide  is  driven  off.  Supposedly 
it  follows  the  analogy  of  the  corresponding  chlorine  and  bromine  com- 
pounds, and  at  temperatures  over  300°  is  changed  to  the  nitride  which 
may  be  reduced  by  heating  with  hydrogen.  The  probable  formation 
of  addition  compounds  with  organic  bases  has  not  been  investigated. 
Stabler  and  Denk  (674)  have  prepared  a  compound  with  ether  which 
has  the  composition  ZrI4.4(C2H5)20. 

Zirconyl  Iodide.  The  normal  salt,  ZrOI2,  has  been  prepared  by 
the  hydrolysis  of  the  tetraiodide  (674).  It  crystallizes  in  colorless 
needles  having  the  composition  ZrOI2.8H20.  These  are  very  hygro- 
scopic and  are  soluble  in  water  or  alcohol.  The  preparation  of  this 
salt  by  dissolving  the  hydroxide  in  hydriodic  acid  presents  several 
difficulties  (742).  Zirconyl  hydroxide  is  scarcely  attacked  by  this 
acid;  hence  the  cold  precipitated  zirconium  hydroxide  must  be  used. 
Even  this  is  only  sparingly  dissolved.  The  best  results  are  obtained 
when  hydrogen  iodide  is  passed  into  water  in  which  the  hydroxide  is 
suspended.  The  evaporation  to  the  crystallizing  point  brings  about 
decomposition  of  the  hydriodic  acid  and  the  crystals  formed  are  col- 
ored with  iodine,  which  is  difficult  to  remove  by  treatment  with  ben- 
zene or  carbon  disulphide.  The  hydrolysis  proceeding  during  these 
operations  brings  about  the  formation  of  basic  salts. 

Basic  Zirconyl  Iodides.    The   compound   ZrO  (OH)  2ZrOI2 .  5H20 


COMPOUNDS  WITH  HALOGENS         75 

has  been  prepared  by  Hinsberg  (337)  by  the  double  decomposition  of 
barium  iodide  with  zirconyl  sulphate  in  solution.  It  is  an  amorphous, 
colorless  powder  which  decomposes  in  the  air,  becoming  colored  with 
iodine.  It  is  soluble  in  water.  A  still  more  basic  substance  was 
obtained  by  Venable  and  Baskerville  (742)  by  the  action  of  hydriodic 
acid  upon  zirconium  hydroxide  suspended  in  water  and  the  evapora- 
tion of  the  solution.  To  limit  the  decomposition  and  separation  of 
iodine  this  evaporation  may  be  carried  out  in  an  atmosphere  of 
carbon  dioxide,  in  which  case  the  salt  ZrOI2.8H20  is  obtained  (674). 
Ordinary  evaporation  gave  a  hard,  hornlike,  colored  mass. 

Zirconyl  lodate.  The  normal  salt,  ZrI03,  has  not  been  prepared. 
Basic  iodates  are  formed  (751)  when  a  solution  of  iodic  acid  is  added 
to  a  solution  of  zirconyl  chloride.  The  white  precipitate  is  quite 
insoluble  in  water  or  dilute  nitric  acid;  hence  the  precipitation  is  prac- 
tically complete,  and  this  has  been  recommended  as  a  means  of  sepa- 
ration for  zirconium  analytically.  A  series  of  basic  zirconyl  iodates 
are  formed  according  to  the  concentration  of  the  solutions  used,  the 
temperature,  and  the  extent  of  the  washing  of  the  precipitate. 

Zirconyl  Periodate.  This  substance  has  been  prepared  by  Weibull 
(794)  as  a  white  precipitate,  insoluble  in  water,  by  adding  a  solution 
of  periodic  acid  to  one  of  zirconyl  chloride.  No  details  are  given  as 
to  composition. 


Chapter  V 

Compounds  with  the  Acids  of  Sulphur  and  Selenium 
Compounds  Formed  with  Sulphurous  Acid 

Zirconium  Sulphite  Zr(S03)2.7H20.  This  has  been  prepared 
(740)  by  suspending  the  hydroxide  in  water  and  saturating  with 
sulphur  dioxide,  separating  the  insoluble  basic  salts  formed,  and 
allowing  the  solution  to  evaporate  to  less  than  one-twentieth  of  its 
bulk  over  sulphuric  acid.  Hard,  white,  warty  crystals  attached  them- 
selves firmly  to  the  sides  of  the  dish.  The  analysis  showed  their 
composition  to  correspond  with  the  above  formula. 

Basic  Zirconyl  Sulphites.  Several  basic  salts  have  been  reported. 
Hermann  (320)  found  that  ammonium  sulphite  gave  a  basic  precipi- 
tate when  added  to  a  solution  of  a  zirconium  salt.  This  was  soluble 
in  an  excess  of  the  ammonium  sulphite.  Zirconium  hydroxide  was  not 
precipitated  from  this  solution  by  alkalies  while  cold,  but  a  precipitate 
formed  on  boiling.  The  formation  of  a  precipitate  on  passing  sulphur 
dioxide  into  a  solution  of  a  zirconyl  salt  was  also  observed  by  Ber- 
thier  (43).  This  precipitate  is  not  readily  formed  if  zirconyl  sulphate 
is  used,  even  after  boiling  (740).  It  forms  readily  when  a  nearly 
neutral  solution  of  zirconyl  chloride  is  used;  especially  after  boiling. 
This  precipitate  varies  in  composition,  the  ratios  of  zirconia  to  sul- 
phur dioxide  in  several  preparations  ranging  from  2  :  1  to  4  :  1,  show- 
ing an  excess  of  base. 

The  precipitation  of  zirconium  by  means  of  sulphur  dioxide  is  not, 
under  ordinary  conditions,  complete  nor  does  it  bring  about  a  complete 
separation  from  iron,  for  which  purpose  it  has  been  recommended, 
but  for  many  purposes  the  degree  of  elimination  of  iron  is  satis- 
factory. 

Zirconyl  Thiosulphate.  Sodium  thiosulphate  forms  a  precipitate 
when  added  to  a  neutral  solution  of  the  chloride  (686).  A  partial 
investigation  of  this  (740)  showed  that  the  precipitate  varied  in  com- 
position according  to  the  extent  of  hydrolysis  and  consisted  of  basic 
forms  of  zirconyl  thiosulphate. 

76 


COMPOUNDS  WITH  THE  ACIDS  OF  SULPHUR          77 

Compounds  with  Sulphuric  Acid 

Normal  Zirconium  Sulphate  (Zr(SOJ2).  This  salt  was  first  pre- 
pared by  Berzelius  (53)  by  heating  zirconia  with  an  excess  of  con- 
centrated sulphuric  acid  and  driving  off  the  excess  of  sulphuric  acid 
below  a  red  heat.  He  reported  it  as  stable  up  to  a  low  red  heat  but 
stated  that  it  decomposed  at  higher  temperatures,  also  that  it  crys- 
tallized from  H2S04  but  better  from  water.  Undoubtedly  a  red  heat 
is  too  high,  and  some  of  the  combined  acid  was  driven  off.  Other 
investigators  (22,  293,  795)  have  shown  that  lower  temperatures  must 
be  used  for  driving  off  the  excess  of  acid,  the  range  being  350°-400°. 
Hauser  (293)  prepared  the  sulphate  by  treating  incompletely  dried 
zirconia,  which  dissolves  more  readily,  with  concentrated  acid  and 
then  driving  off  the  excess  acid  at  360°-380°.  This  may  be  done 
conveniently  in  a  Kjeldahl  flask  over  which  is  fitted  a  small  funnel 
connected  with  a  suction  pump  for  carrying  off  the  fumes  and  pre- 
venting the  access  of  dust.  Dried  zirconia  is  acted  upon  slowly  and 
with  difficulty,  and  ignited  zirconia  is  scarcely  attacked  at  all.  The 
salt  is  quite  stable  and  only  traces  of  the  combined  acid  are  lost  after 
heating  at  380°  for  eight  to  ten  hours.  If  a  gas  burner  is  used  for 
the  heating  the  product  must  be  protected  from  the  water  formed  in 
the  combustion  of  the  gas,  as  this  partially  hydrolyzes  the  sulphate. 

The  neutral  water-free  sulphate  dissolves  slowly  in  water,  evolv- 
ing a  considerable  amount  of  heat.  This  Hauser  (293)  attributed  to  the 
formation  of  the  tetrahydrate,  Zr(S04)2  +  4H20  =  Zr(SOJ2.4H2O, 
which  then  dissolves  without  heat  evolution  but  is  hydrolyzed  to 
zirconyl  sulphate.  The  heat  of  formation  from  the  action  of  sul- 
phuric acid  upon  the  hydroxide  is  given  by  Pissarjewski  (554)  as 
11,670  cal.  The  tetrahydrate  Zr(SOJ2.4H20  forms  rhombic  or  small 
tabular  crystals.  It  is  insoluble  in  alcohol.  Three  molecules  of 
water  are  lost  on  heating  at  100°-120°,  the  fourth  only  on  prolonged 
heating  at  a  higher  temperature  short  of  decomposition  (536,  610). 
On  slow  concentration  of  a  solution  of  zirconium  sulphate  containing 
an  excess  of  sulphuric  acid  a  crystalline  crust  is  formed.  This  retains 
water  of  crystallization.  When  an  aqueous  solution  to  which  no 
acid  has  been  added  is  evaporated  the  hydrolysis  is  far-reaching  and 
a  gumlike  mass  is  left.  Sulphur  trioxide  is  driven  off  on  ignition  of 
the  sulphate,  but  heating  for  some  time  at  a  temperature  of  900°- 
1000°  fails  to  remove  the  last  traces.  Bailey  (22)  heated  it  with 
ammonium  carbonate  in  order  to  remove  the  last  of  the  sulphur  tri- 


78  ZIRCONIUM  AND  ITS  COMPOUNDS 

oxide  but  according  to  other  investigators  this  involved  the  loss  of 
some  zirconia.  The  anhydrid  2ZrO.S03  is  left  when  the  sulphate  is 
heated  for  some  time  at  200°-300°  in  the  presence  of  water  vapor. 
This  is  commonly  found  in  commercial  preparations  of  the  sulphate. 

The  normal  zirconium  sulphate  is  readily  hydrolyzed  when  dis- 
solved in  water,  giving  a  strong  acid  reaction.  The  extent  of  this 
hydrolysis  depends  upon  the  extent  of  the  dilution,  the  time  elapsed, 
and  the  temperature.  For  instance,  the  specific  conductivity  of  a 
1.75  p.c.  solution  at  18°  when  determined  immediately  after  prepara- 
tion was  found  by  Ruer  and  Levin  (621)  to  be  3105X10'5  ohmXc.c.-1. 
After  twenty  hours  it  was  3186;  after  boiling  3418.  Twenty-four 
hours  later  it  was  3432  and  this  had  not  changed  after  standing 
seventy-two  hours.  Very  dilute  solutions  become  opalescent  on  boil- 
ing and  the  hydroxide  separates.  These 'become  clear  again  on  con- 
centration. The  work  of  Venable  and  Jackson  (750)  would  indicate 
that  on  dissolving  the  normal  sulphate  Zr(S04)2  at  0°  and  also  at 
20°  there  was  for  the  first  three  observations  taken  at  5-minute 
intervals  a  slight  increase  of  resistance  followed  by  a  slow  decrease 
for  three  hours.  After  that  an  equilibrium  was  reached.  The  be- 
havior in  the  first  15  minutes  was  doubtless  due  to  change  in  reach- 
ing a  temperature  equilibrium.  The  addition  of  alcohol  to  solutions 
of  the  normal  sulphate  causes  the  precipitation  of  basic  zirconyl  salts. 
Crystalline  basic  salts  also  form  under  certain  conditions  of  dilution 
and  temperature  (295)  and  the  boiling  of  dilute  solutions  gives  pre- 
cipitates of  basic  compounds  (601). 

Acid  Sulphates  or  Zircon-Sulphuric  Acid.  The  existence  of  such 
compounds  for  the  normal  sulphate  has  been  questioned  but  seems 
probable.  The  subject  was  brought  under  investigation  by  the  dif- 
ference shown  by  the  sulphate  from  certain  other  zirconium  salts  in 
its  behavior  towards  various  reagents,  such  as  oxalic  acid  or  am- 
monium oxalate.  This  has  been  studied  by  a  number  of  investigators 
and  several  theories  have  been  formulated  as  to  the  constitution  of 
the  sulphate  when  dissolved.  Hauser  (296)  found  that  the  solubility 
of  the  sulphate  in  H2S04  decreased  with  the  increase  of  concentration 
of  the  acid  up  to  a  certain  point  and  then  suddenly  and  notably  in- 
creased to  a  point  at  which  a  slightly  increased  concentration  de- 
creased the  rate  of  solution.  By  using  a  concentration  greater  than 
61.4  p.c.  there  may  be  obtained  a  clear  liquid  which,  on  standing  a 
number  of  days,  deposits  fine,  monoclinic,  needlelike  crystals  quite  dif- 
ferent in  form  from  those  of  the  salt  Zr(S04)2.4H20.  The  analysis  cor- 


COMPOUNDS  WITH  THE  ACIDS  OF  SULPHUR  79 

responded  to  the  composition  Zr(SO4)2.H2S04.3H2O.  The  formation 
of  these  crystals  is  easy  to  overlook  as  they  crystallize  slowly.  The 
exact  conditions  for  their  formation  are  as  follows:  The  tetrahydrate, 
Zr(S04)2.4H20,  is  practically  insoluble  in  water  containing  45-55  p.c. 
of  S03;  with  more  than  57  p.c.  there  is  a  rapid  increase  in  solu- 
bility. The  reaction,  as  stated  by  Hauser,  Zr(SOJ2.4H20±^ 
Zr(S04)2.H2S04.3H20,  takes  place  at  39.5°  and  a  concentration  of 
61.4  p.c.  S03.  On  melting  this  trihydrate  with  much  concentrated 
H2S04  in  a  glass  tube  and  allowing  it  to  stand  for  some  days  a  com- 
pact, crystalline  powder,  which  on  analysis  gave  the  monohydrate 
Zr(SO4)2.H2S04.H2O,  is  formed.  These  hydrates  Hauser  called  hy- 
drates of  zircon-sulphuric  acid,  Zr(SO4)2.H2S04.  He  also  noted  that 
the  boiling  points  of  solutions  of  Zr(S04)2.4H20  in  concentrated 
H2S04  slowly  but  materially  fall  on  heating,  and  basic  zirconyl  salts 
separate  as  crystals  or  precipitates.  In  the  electrolysis  of  this  zircon- 
sulphuric  acid  the  zirconium  formed  a  complex  anion.  Thus 

H2[Zr(S04)]3  *±  2H,  Zr(S04)3.  The  behavior  under  electrolysis 
would  manifestly  depend  largely  upon  the  dilution,  and  the  presence 
of  water  brings  about  hydrolysis.  It  is  quite  possible,  therefore,  for 
the  solid  salt  to  be  zirconium  bisulphate.  Double  salts  have  been 
obtained  with  the  alkaline  sulphates. 

Ruer  (617)  in  his  investigation  of  the  constitution  of  zirconium 
sulphate  tetrahydrate  reached  the  conclusion  that  in  aqueous  solution 
the  formula  should  be  ZrOS04.H2S04,  which  undergoes  a  progressive 
further  hydrolysis  unless  excess  of  acid  is  present.  Further,  he  con- 
tended that  in  the  crystalline  form  the  constitution  is  to  be  expressed 
by  the  formula  ZrOS04.H2S04.3H2O.  He  found  the  electrical  dis- 
sociation in  solution  to  be  ZrOSO4 .  H2SO4  <=±  2H,  ZrO(S04)2,  the 
zirconium  migrating  with  the  negative  stream.  Double  salts  with 
sodium,  as  Na2S04 .  ZrOSO4,  dissociate  in  the  same  way.  It  has  been 
shown  also  that  the  supposed  ZrS04.4H2O  loses  three  molecules  of 
water  at  100°,  the  fourth  molecule  being  lost  only  after  prolonged 
heating  at  a  higher  temperature,  indicating  the  absorption  of  energy 
in  the  dissociation  of  the  molecule  and  re-formation  of  water.  Chau- 
venet  and  Gueylard  (134)  found  that  cryoscopic  measurements  gave 
the  molecular  weight  of  the  sulphate  in  solution  as  79.4  instead  of 
286.6,  or  approximately  four  independent  particles  to  the  molecule. 
Analysis  gave  the  probable  form  as  ZrOS04.H2S04.  Conductivity 


80  ZIRCONIUM  AND  ITS  COMPOUNDS 

experiments  during  neutralization  with  NaOH  indicated  the  presence 
of  three  compounds,  ZrOS04,  ZrOS04.Zr02,  and  3ZrOS04.Zr02. 

The  addition  of  alcohol  to  the  solution  of  the  sulphate  gives  basic 
precipitates.  The  objection  may  be  raised  here  that  the  alcohol 
itself  has  a  hydrolyzing  effect.  The  use  of  ether,  which  is  not  open 
to  this  objection,  also  yields  strongly  basic  compounds.  Rosenheim 
and  Frank  (609)  assumed,  on  the  basis  of  their  experiments,  the 
existence  of  an  equilibrium  2ZrO(S04H)2  +  H20  ±^Zr203(S04H)2 
+  2H2S04.  Other  work  bearing  on  this  subject  may  be  found  in 
references  568,  570,  38,  561. 

The  mass  of  evidence  would  go  to  show  that  zirconium  sulphate, 
Zr(S04)2,  exists  only  in  the  entire  absence  of  water.  The  normal  sul- 
phate dissolves  slowly  in  water.  Attempts  at  making  a  one-fifth 
molar  solution  at  0°  left  a  portion  undissolved,  but  the  one-tenth 
molar  was  made,  evolving  considerable  heat  and  requiring  some  15 
minutes  for  temperature  adjustment  (750).  The  hydrolysis  then 
progresses,  reaching  apparently  an  equilibrium  after  3-4  hours,  or 
at  least  a  point  at  which  the  velocity  of  reaction  is  very  slight.  The 
velocity  also  diminishes  with  decreasing  temperature.  Basic  salts 
may  settle  out  and  these  will  be  described  under  that  heading  (296). 
The  normal  sulphate  crystallizes  from  concentrated  H2S04  without 
change.  With  a  concentration  of  50-60  p.c.  S03  the  bisulphate 
crystallizes.  Below  that  concentration  zirconyl  acid  sulphate, 
ZrOSO4.H2S04..3H20,  is  obtained  in  crystalline  form.  With  still 
greater  dilution  crystalline  basic  zirconyl  salts  are  formed. 

Double  Salts  of  Zirconium  Sulphate  with  the  Alkaline  Sulphates. 
Rosenheim  and  Pinksker  (612)  have  reported  that  normally  consti- 
tuted double  alkali  sulphates  separate  from  a  solution  of  Zr(S04)2  in 
H2S04  on  the  addition  of  solutions  of  the  alkali  sulphates.  These  are 
regarded  as  derivatives  of  H4(Zr(S04)4).  They  may  also  be  looked 
upon  as  double  salts  with  zirconium  bisulphate,  K2S04..ZrH2(S04)3. 
They  undergo  hydrolysis  in  water. 

The  normal  double  sulphate,  2K2S04.Zr(S04)2.3H20,  which  may 
be  written  as  the  potassium  salt  of  the  above  complex  acid,  is  formed 
when  potassium  bisulphate  in  concentrated  solution  and  at  boiling 
temperature  is  saturated  with  Zr(OH)4,  freshly  precipitated  in  the 
cold  (609,  610) .  The  salt  forms  in  very  soluble,  needlelike  crystals. 
Analogous  salts  of  sodium  and  ammonium  have  also  been  formed. 
When  KHS04  is  added  to  a  solution  of  Zr(S04)2  basic  zirconyl  sul- 
phates form. 


COMPOUNDS  WITH  THE  ACIDS  OF  SULPHUR  81 

Zirconyl  Sulphate.  Berzelius  (53),  by  saturating  a  solution  of 
zirconium  sulphate  with  the  hydroxide  and  evaporating,  obtained  a 
gumlike  mass  which  became  white  on  drying.  On  further  heating  it 
intumesced  and  lost  water.  On  ignition  it  lost  additional  water  and 
S03.  The  analysis  gave  the  ratio  Zr02  :  S03  : :  100  :  65.9.  The 
original  gum  could  be  dissolved  in  a  small  amount  of  water  but  gave 
a  precipitate  on  the  further  addition  of  water.  From  a  similar  solu- 
tion-by  neutralizing  with  ammonia  Kulka  (417)  prepared  a  gela- 
tinous substance  having  the  same  composition.  The  gummy  mass 
separated  out  and  was  soluble  in  water  but  insoluble  in  acid.  Ac- 
cording to  the  view  of  Hauser  (292),  these  were  to  be  regarded  as 
solutions  of  the  colloidal  hydroxide  in  the  neutral  sulphate.  He 
found  that  fresh  cold-precipitated  hydroxide,  which  is  largely 
Zr(OH)4,  dissolved  more  easily.  Concentrated  solutions  of  the  sul- 
phate digested  at  60°  with  this  hydroxide  for  several  days  gave  a 
solution  ,  containing  Zr02  :  S03  ::  1.15  :  1.  Other  investigators  have 
reported  this  ratio  as  1  :  1.  Much  less  of  the  hot-precipitated  hydrox- 
ide is  dissolved.  Zirconyl  sulphate  was  not  obtained  on  evaporating 
this  solution. 

Though  zirconyl  sulphate  ZrOS04  is  doubtless  the  first  stage  in 
the  hydrolysis  of  the  sulphate,  it  seems  to  be  quickly  converted  into 
basic  salts  and  no  account  of  its  separation  has  been  given  that  is 
not  open  to  criticism.  As  has  been  already  shown,  the  crystalline 
tetrahydrate  ZrS04)2.4H20  should  have  assigned  to  it  the  formula 
ZrOS04.H2S04.3H20,  and  hence  may  be  regarded  as  the  hydrate  of 
a  zirconyl  sulphuric  acid  or  of  the  acid  zirconyl  sulphate  whose  for- 

H\ 

S04 
mula  would  be  ZrO<         .    This  corresponds  to  zircon-sulphuric  acid 

S04 
H/ 

H>S04 

or  acid  zirconium  sulphate  Zr  =  S04. 

H>S04 

Zirconyl  sulphate  is  reported  by  Chauvenet  (130)  as  water-free 
ZrOS04  and  in  the  following  hydrates:  ZrOS04.4H20;  ZrOS04.2H20; 
ZrOS04.H20.  The  acid  sulphate  is  given  as  ZrOS04.S03; 
ZrOS04.S03.H20;  ZrOSO4.S03.4H20. 

Basic  Zirconyl  Sulphates.  The  boiling  points  of  solutions  of 
ZrOS04 .  H2S04 .  3H20  in  H2S04  decrease  slowly  but  materially  on  pro- 
longed heating.  This,  according  to  Hauser  (296) ,  is  to  be  referred 


82  ZIRCONIUM  AND  ITS  COMPOUNDS 

to  the  formation  of  a  basic  salt,  2Zr02.3S03.5H20,  which  separates 
in  crystalline  form  from  very  concentrated  solutions.  Less  concen- 
trated solutions  give  a  flocculent  precipitate  on  boiling.  This  deposi- 
tion of  crystals  causes  a  fall  in  temperature.  At  a  definite  dilution 
the  basic  salt,  4Zr02.3S03.14H20,  separates,  the  extent  of  dilution 
necessary  depending  upon  the  temperature.  With  increase  of  tem- 
perature a  greater  dilution  becomes  necessary  and  on  very  great 
dilution  no  precipitation  is  observed.  The  velocity  of  the  reaction 
is  slight  and  diminishes  with  decreasing  temperature  so  that  the  solu- 
tion may  require  prolonged  standing  for  the  detection  of  the  deposit. 
It  is  best  observed  at  a  temperature  of  39.5°.  As  reported  by  Hauser, 
the  solution  remained  clear  for  dilutions  Zr(S04)2  :  H20  : :  3  :  8.3  : : 
3  :  10  ::  3  :  16,  but  precipitation  began  at  3  : 20  and  continued  up  to 
a  dilution  of  1  :  120  after  standing  for  ten  hours  at  39.5°.  The  crys- 
talline salt,  4Zr02.3S03.14H20,  was  therefore  not  decomposed  at 
that  temperature  and  dilution.  Its  solubility  is  less  than  0.009  p.c. 
It  was  found  that  the  original  salt  had  been  hydrolyzed  in  this  way 
to  the  extent  of  66-67  p.c.  of  the  total.  Dilute  H2S04  dissolves  this 
salt  very  slowly,  concentrated  acid  readily.  The  element  of  time  in 
this  change  is  important,  and  ranges  for  dilute  solutions  from  two  to 
five  days.  From  these  observations  it  will  be  seen  that  the  nature 
of  a  solution  of  zirconyl  sulphate  depends  largely  upon  its  previous 
history.  It  may  be  noted  that  the  formula  for  this  basic  salt  may 
also  be  written  ZrO(OH)2.3ZrOS04.13H20  in  agreement  with  the 
analysis  and  also  with  the  fact  that  very  dilute  solutions  are  opales- 
cent and  yield  the  colloidal  hydroxide  ZrO(OH)2  on  being  dialyzed. 
Very  dilute  solutions  of  this  basic  sulphate  which  have  been  heated 
for  a  time  at  64°  have  lost  the  power  of  forming  the  crystalline  deposit 
when  allowed  to  stand  at  a  lower  temperature.  They  also  show 
analytical  differences.  No  immediate  precipitate  is  given  with  H202 
but  only  after  standing.  Oxalic  acid  in  small  amount  also  gives 
none.  The  formation  of  this  indifferent  stage  seemed  to  depend  in 
large  measure  upon  the  concentration.  Concentrated  solutions  after 
being  heated  and  then  diluted  behaved  differently  from  those  which 
were  first  diluted  and  then  heated  (296) . 

A  basic  salt,  2Zr02 .  3S03 .  5H20,  crystallized  from  very  concen- 
trated solutions  and  a  flocculent  precipitate,  doubtless  without  defi- 
nite composition,  separated  from  quite  dilute  solutions.  This  latter 
is  very  slightly  soluble  in  water,  giving  a  weakly  acid  reaction.  It 
is  slowly  dissolved  in  dilute  H2S04  but  rapidly  dissolved  when  the 


COMPOUNDS  WITH  THE  ACIDS  OF  SULPHUR  83 

acid  has  a  30  p.c.  concentration.     On  drying  at  300°  the  composition 
was  2Zr02.3S03,  Hauser  (293). 

According  to  Berzelius  (53),  a  flocculent  basic  substance  with  the 
composition  3Zr02.2S03  is  formed  when  alcohol  is  added  to  a  solu- 
tion of  the  sulphate.  Paykull  (536)  prepared  a  substance  having  a 
similar  composition  as  a  fine-grained  precipitate  by  considerably 
diluting  the  solution  and  washing  the  precipitate  with  boiling  water. 
This  was  insoluble  in  water  and  soluble  in  hydrochloric  acid,  and  was 
hydrated.  The  formula  was  calculated  on  the  dry  basis.  Endemann 
(209)  using  alcohol  as  a  precipitant  and  very  concentrated  aqueous 
solutions  of  the  sulphate,  prepared  a  basic  substance  having  the  com- 
position 7Zr02 .  6S03 . 14H20,  which  retained  some  of  the  alcohol.  The 
addition  of  very  little  water  freed  the  alcohol;  more  cold  water  dis- 
solved the  precipitate ;  and  on  driving  off  the  water  an  amorphous  mass 
was  left.  If  much  water  was  used  in  dissolving  an  insoluble  basic  salt 
separated.  There  is  little  evidence  that  these  compounds  were  not 
mere  mixtures. 

Chauvenet  (128,  130),  by  determining  the  densities  in  nitrobenzene 
at  12.4°,  obtained  a  curve  with  composition  and  density  as  the  coordi- 
nates. This  gave  six  points  of  inflection  corresponding  to  the  basic 
salts  Zr(S04)2;  Zr(S04)2.Zr02;  5Zr(S04)2.7Zr02;  3Zr(S04)  .5Zr02; 
Zr(S04)2.3Zr02;  and  Zr(SOJ2.2Zr02. 

Patents  have  been  issued  for  methods  of  preparation  of  a  basic 
sulphate  5Zr02.2S03.14H20  (608)  and  also  one  having  the  composi- 
tion 5Zr02 .  3S03 . 13H20. 

Hauser  and  Herzfeld  (300)  have  ascribed  the  following  hypo- 
thetical formulas  to  the  basic  sulphates  obtained  by  them.  One  com- 
pound crystallized  in  needles  having  parallel  extinction.  The  com- 
position was  Zr4(S04)3(OH)10.10H20.  Another  compound  obtained 
in  spheroidal  crystals  had  the  formula  [ZrJS04)2(OH)11]2.S04.8H20 
assigned  to  it.  Also  there  were  the  compounds 

[Zr4(S04)6(OH)6]H4.4H20  and  [Zr4(S04)5(OH)8]H2. 
The  only  double  compound  prepared  in  a  pure  form  was  obtained  by 
dissolving  Zr(S04)2.10H20  in  15  c.c.  of  water,  adding  1  c.c.  of  con- 
centrated H2S04,  and  then  adding  dropwise,  without  stirring,  a  con- 
centrated solution  of  K2S04  until  the  original  precipitate  almost  dis- 
appeared, leaving  a  cloudy  liquid.  The  formula  assigned  the  crystal- 
line deposit  was  K2Zr4(S04)5(OH)8. 

Double  Salts  of  Zirconyl  Sulphate  with  the  Alkali  Sulphates. 
When  potassium  sulphate,  either  in  crystals  or  in  saturated  solution, 


84  ZIRCONIUM  AND  ITS  COMPOUNDS 

is  added  in  excess  to  a  solution  of  zirconyl  sulphate  all  of  the  zir- 
conium is  gradually  precipitated  as  a  crystalline  double  salt  of  vary- 
ing composition.  The  excess  of  the  potassium  sulphate  remaining 
in  the  solution  is  changed  partly  into  the  bisulphate.  The  composi- 
tion of  the  basic  double  salt  depends  upon  the  extent  to  which  the 
hydrolysis  of  the  zirconyl  sulphate  had  gone  and  also  upon  other 
conditions.  Such  basic  precipitates  are  formed  also  on  the  addition 
of  other  salts  of  potassium.  These  crystalline  precipitates  are  diffi- 
cultly soluble  in  water  and  may  be  reprecipitated  by  the  addition  of 
K2S04.  They  are  fairly  soluble  in  acids  if  they  have  been  only 
slightly  washed  in  water.  If  thoroughly  washed  they  become  prac- 
tically insoluble  in  water  or  dilute  acid.  These  basic  double  sulphates 
are  decomposed  by  ammonia  and  are  soluble  in  ammonium  carbonate. 
By  washing  with  water  they  are  separated  into  a  soluble  substance 
richer  in  sulphuric  acid  and  an  insoluble  one  that  is  poorer.  The 
solution  of  the  former  forms  an  abundant  crystalline  precipitate  after 
standing  a  few  days  (760). 

Rosenheim  and  Frank  (609)  prepared  certain  double  salts  with 
alkali  sulphates  which,  they  stated,  might  be  regarded  as  alkali  salts 
of  a  basic  zirconyl  sulphuric  acid,  Zr203(S04H)2.  These  were  ob- 
tained by  precipitating  cold  concentrated  solutions  of  Zr(S04)2  and  an 
alkali  sulphate  with  alcohol  and  washing  with  a  little  alcohol  and 
ether.  The  product  was  quite  homogeneous  and  consisted  of  very 
small,  probably  tabular  crystals.  They  could  not  be  recrystallized  but 
suffered  change  on  treatment  with  water.  The  following  double 
salts  were  prepared:  Zr203(S04K)2.8H20;  Zr203(S04Rb)2.15H20; 
Zr203(S04Cs)2.llH20.  No  analogous  salts  were  obtained  with 
sodium  and  ammonium  salts  but  amorphous  basic  products  only. 
These  salts  presuppose  the  existence  of  a  complex  anion  Zr203(S04)2. 
Hauser  and  Herzfeld  (300)  have  denied  the  accuracy  of  Ruer's  work 
(621)  and  the  existence  of  the  complex  anions  ZrO(S04)2  and 
Zr203(S04)2. 

According  to  Chauvenet  and  Gueylard  (134),  evidence  was  ob- 
tained by  cryoscopic  and  thermochemical  methods  of  the  existence 
of  the  following  double  compounds:  2ZrOS04.S03.3Na2S04.8H20; 
3ZrOS04 .  S03 .  2Na2S04 .  7H20 ;  ZrOS04 .  S03 .  (NH4 )  2S04 .  3H20 ;  and 
ZrOS04.S03.2(NH4)2S04.3H2O.  Also  the  following:  3ZrOS04.2M2S04 
and  3ZrOS04..M2S04  where  M  represents  K,  Na  or  NH4. 

The  complex  and  varying  products  obtained  by  mixing  a  solution 
of  zirconyl  sulphate  with  one  of  potassium  sulphate  have  long  been 


COMPOUNDS  WITH  THE  ACIDS  OF  SULPHUR          85 

a  puzzle.  In  part,  at  least,  mixtures  of  hydrolyzed  substances  are 
formed.  Recently  it  has  been  shown  (298)  that  if  the  mixed  solu- 
tions are  concentrated  over  sulphuric  acid  definite  compounds  crys- 
tallize. These  show  very  well  the  influence  of  such  a  salt  as  potas- 
sium sulphate  upon  a  progressing  hydrolysis.  When  potassium  sul- 
phate is  used  micro-crystalline  needles  whose  composition  is 
K4Zr4(OH)8(S04)5.8H20  are  obtained.  In  a  solution  strongly  acid 
with  sulphuric  acid  the  first  crystals  formed  are  K4Zr(S04)4;  in 
weakly  acid  solutions  the  composition  is  that  of  potassium  zirconium 
hydroxysulphate  of  varying  composition.  These  products  hydrolyze 
on  being  treated  with  water.  If  boiled  with  water,  they  become 
opalescent  with  colloidal  zirconium  hydroxide.  Following  the  crystal- 
lizations in  detail,  the  above-mentioned  potassium  zirconium  hydroxy- 
sulphate, K4Zr4(OH)8(S04)5.8H20,  forms  a  crystalline  crust  of 
needles.  A  second  crop  of  prismatic  crystals  is  formed  and  these 
have  the  composition  K4Zr(S04)4.5H20.  The  first  crystals  hydro- 
lyze to  increase  the  free  acid  and  bring  about  an  equilibrium.  The 
formation  of  the  second  then  begins  and  decreases  the  amount  of 
free  acid.  The  reaction  is  thereupon  reversed  and  the  hydroxysul- 
phate crystals  form  once  more. 

Compounds  with  Selenious  Acid 

Zirconium  Selenite.  According  to  Berzelius  (52)  this  is  a  white 
powder  soluble  in  an  excess  of  selenious  acid.  The  basic  zirconyl 
selenite,  4Zr02.3Se02.18H20,  was  prepared  by  Nilson  (517)  by  pre- 
cipitating a  solution  of  zirconyl  chloride  with  sodium  selenite.  Kulka 
(417)  claimed  to  have  prepared  the  same  salt  by  adding  a  solution 
of  selenium  dioxide  in  nitric  acid  to  a  solution  of  Zr(SOJ2.  It  was 
described  as  a  jelly  like  precipitate  soluble  in  hydrochloric  acid.  At 
100°  it  lost  fifteen  molecules  of  water.  Weibull  (795)  found  this 
precipitate  to  have  on  drying  the  composition  Zr02 .  Se02 .  2H20. 

The  normal  selenite  Zr(Se03)2  is  reported  by  Nilson  (517)  as 
being  formed  when  the  above  basic  salt,  4Zr02.3Se02.18H20,  is 
digested  with  selenious  acid  at  60°.  The  amorphous  or  colloidal  pre- 
cipitate is  changed  into  microscopic  crystals  in  the  form  of  four-sided 
columns  with  sharply  cut  ends.  This  form  is  retained  when  they  are 
heated  to  a  temperature  at  which  the  selenium  dioxide  is  driven  off. 
They  are  difficultly  soluble  in  hot  hydrochloric  acid,  some  of  the 
selenium  being  volatilized  as  chloride.  If  a  concentrated  solution  of 


86  ZIRCONIUM  AND  ITS  COMPOUNDS 

selenium  dioxide  is  used  the  crystals  are  water-free  and  have  the 
composition  Zr(Se03)2.  With  a  more  dilute  solution  one  molecule 
of  water  of  crystallization  is  present,  Zr(Se03)2.H20.  This  is  prob- 
ably a  zirconyl  salt  following  the  analogy  of  the  sulphite. 

Selenious  acid  has  been  recommended  by  Smith  and  Jones  (664) 
as  a  means  of  separating  and  determining  zirconium. 

Compounds  with  Selenic  Acid 

Zirconium  Selenate.  This  salt  has  been  obtained  by  Weibull 
(795)  as  the  tetrahydrate  having  the  formula  Zr(SeOJ2.4H20,  thus 
corresponding  to  the  normal  sulphate  and  probably  being  hydrolyzed 
in  the  same  way.  It  was  prepared  by  dissolving  zirconium  hydroxide 
in  selenic  acid.  It  crystallized  in  transparent  four  and  six-sided 
tables  of  the  hexagonal  system.  Three  molecules  of  water  are  lost 
at  100°,  the  fourth  between  120°  and  130°.  The  water-free  salt  is 
only  slightly  hygroscopic.  It  is  soluble  in  water  but  only  slightly 
soluble  in  concentrated  acids  or  alcohol.  Weibull  also  obtained  basic 
products  by  hydrolyzing  the  normal  salt  with  boiling  water. 

Compounds  with  the  Oxy acids  of  Tellurium 

The  compounds  with  these  acids  have  been  investigated  only  by 
Berzelius  (59,  60).  He  reported  the  tellurite  as  a  white,  flocculent 
precipitate  and  the  tellurate  as  a  bulky,  semi-transparent  mass  solu- 
ble in  an  excess  of  the  zirconyl  chloride  solution  from  which  it  was 
prepared.  The  method  of  preparation  was  by  the  addition  of  a 
solution  of  sodium  tellurite  or,  respectively,  the  tellurate  to  the  solu- 
tion of  a  zirconium  salt  such  as  the  chloride. 


Chapter  VI 

Compounds  with  Acids  of  the  Nitrogen  Group  and  Eare 

Inorganic  Acids 

Compounds  with  Nitric  Acid 

Berzelius  (52)  observed  that  a  solution  of  zirconium  hydroxide 
in  nitric  acid  left  on  evaporation  a  yellow  gummy  mass  which  lost 
its  acid  radical  on  heating.  If  the  heating  was  not  carried  beyond 
100°  the  residue  was  completely  soluble  in  water  and  the  solution 
had  the  capacity  of  taking  up  still  more  hydroxide  or  could  be  neu- 
tralized with  much  alkali  before  a  permanent  precipitate  was  formed. 
Mandl  (466)  failed  to  prepare  a  neutral  salt  by  the  concentration  of 
such  a  solution  or  a  double  salt  by  adding  potassium  nitrate.  Miiller 
(512)  found  no  nitrate  of  constant  composition  but  obtained  always 
a  mixture  of  the  nitrate  and  the  hydroxide  formed  during  the  hydrol- 
ysis, this  hydroxide  going  into  colloidal  solution.  Rosenheim  and 
Frank  (610)  could  obtain  only  zirconyl  nitrate,  ZrO(N03)2.2H20, 
which  crystallized  in  well-defined  forms.  These,  reduced  to  a  fine 
powder,  were  dissolved  by  prolonged  boiling  in  absolute  alcohol,  and 
from  this  solution  ether  precipitated  a  white  powder.  This  was  easily 
soluble  in  water  and  had  the  composition  Zr203(N03)2.5H20  or 
ZrO(OH)2.ZrO(N03)2.4H20.  Other  observations  reported  by  Her- 
mann (320),  Paykull  (537),  and  Weibull  (794)  are  manifestly  errone- 
ous from  a  failure  to  take  into  account  the  changes  brought  about 
by  hydrolysis  in  the  solutions.  The  zirconium  nitrate  of  commerce 
is  more  or  less  basic  zirconyl  nitrate. 

Chauvenet  and  Nicolle  (135)  have  repeated  some  of  these  earlier 
experiments.  The  concentration  of  a  solution  of  zirconium  hydroxide 
in  nitric  acid  over  caustic  potash  did  not  yield  the  normal  nitrate, 
nor  did  the  evaporation  of  a  syrupy  solution  at  a  low  temperature 
in  a  current  of  carbon  dioxide  charged  with  oxides  of  nitrogen.  The 
latter  yielded  only  zirconyl  nitrate.  They  concluded  that  the  exist- 
ence of  the  normal  nitrate  was  doubtful.  Certainly,  if  formed,  it  is 
most  easily  and  rapidly  hydrolyzed.  They  found  that  the  methods 
hitherto  used  yielded  only  the  zirconyl  nitrate  which  crystallizes  with 
two  molecules  of  water.  This  remains  unaltered  in  the  air  and  does 

87 


88  ZIRCONIUM  AND  ITS  COMPOUNDS 

not  fume  if  entirely  freed  from  adhering  nitric  acid.  Efforts  at  dehy- 
dration even  at  the  lowest  possible  temperature  and  in  a  current  of 
carbon  dioxide  saturated  with  oxides  of  nitrogen  failed,  as  some  nitric 
acid  always  accompanied  the  water  driven  off. 

The  possible  existence  of  other  hydrates  was  investigated  (135) 
by  preparing  various  mixtures  of  ZrO(N03)2.2H2O  with  water  and 
measuring  the  heat  of  fixation  of  n  molecules  of  water  to  the  dihy- 
drate. 

ZrO(N03)a.2H20  — aq.  =  ZrO(N03)2diss.    +  2.17  cal. 


.3H20  " 
3.5H2O  " 
4.17H2O  " 
4.76H.O  " 


—  0.50 

—  1.92 

—  2.77 

—  3.95 


6H2O  "         =  -^5.90    ' 

The  curve  constructed  with  these  data  gave  only  one  angular  point 
corresponding  to  ZrO(N03)2.3.5H20.  This  hydrate  forms  at  0°,  is 
unstable  at  10°,  and  effloresces  rapidly  at  ordinary  temperature,  yield- 
ing the  dihydrate.  Anhydrous  zirconyl  nitrate,  according  to  these 
investigators,  does  not  exist. 

The  effect  of  dilution  on  zirconyl  nitrate  was  also  examined  (136). 
The  dihydrate  is  very  soluble  and  hydrolyzes  immediately.  The  ex- 
tent of  this  hydrolysis  was  measured  by  conductivity  determinations 
on  a  N/100  solution  at  29.5°. 

Some  minutes  after  preparation  ^505.19 
"      hours          "  "  554. 

"      days  600. 

At  this  point  it  was  apparently  constant,  remaining  stationary  for 
some  months.  There  slowly  formed  a  precipitate  having  the  compo- 
sition ZrO(N03)2.Zr02.  (H20)n,  which  may  also  be  written 
ZrO(OH)2.ZrO(N03)2.H20)n-1.  Of  course,  a  number  of  reactions  are 
possible  in  the  changes  measured  above.  An  effort  was  made  to  deter- 
mine these  by  neutralizing  the  liberated  acid  with  N/100  NaOH  and 
following  up  the  neutralization  by  measuring  the  resistance.  Por- 
tions (5  c.c.)  of  the  zirconyl  nitrate  N/100  solution  were  taken.  The 
results  were  as  follows: 

ZrO(N03)2.2H20  NaOH  W. 

5  0  257 

5  2  302 

5  4  344 

5  5  373 

5  6  407 

5  7  437 

5  8  470 

5  10  545 

5  12  487 

5  14  411 


COMPOUNDS  WITH  ACIDS  OF  NITROGEN  GROUP      89 

Examination  of  the  curve  constructed  from  these  data  indicated  the 
presence  of  two  angular  points  corresponding  to  the  two  reactions 
ZrO(N03)2  +  NaOH  =  NaNO3  +  ZrONO3  and  ZrO(NO3)2+2NaOH 
=  2NaN03  +  Zr02.  From  this  the  inference  was  drawn  that  the 
constitution  of  the  zirconyl  solution  in  dissociating  was 
Zr(OH)3N03.HNO3.  Cryoscopic  measurements  gave  the  molecular 
weight  as  92.9  instead  of  266.6,  which  meant  that  the  number  of 
independent  particles  probably  numbered  three.  This  is  a  helpful 
clue  toward  the  solution  of  the  problem,  but  of  course  leaves  the 
identity  of  the  independent  particles  unsettled.  As  to  the  progressive 
dehydration  of  the  crystals  by  heat,  it  was  found  that  dissociation 
began  at  120°  even  in  the  presence  of  oxides  of  nitrogen.  At  this 
temperature  a  fairly  constant  weight  can  be  obtained  and  the  results 
indicated  the  presence  of  the  basic  nitrate  Zr02.3ZrO(N03)2,  as  in 
the  case  of  the  sulphate.  If  dehydrated  in  air  at  110°  the  substance 
Zr09.2ZrO(N03)2.7H2O  was  left;  at  150°,  2Zr02.ZrO(N03)2.4H2O; 
at  215°,  7Zr02.ZrO(N03)2.5H20;  at  250°,  10ZrO2.ZrO(N03)2.4H20; 
and  at  300°  dissociation  was  complete  with  the  formation  of  the  end 
product  Zr02. 

Wagner  (756)  has  examined  what  he  called  the  temporary  hydrol- 
ysis of  zirconyl  nitrate  solutions  with  the  aid  of  the  ultramicroscope. 
Biltz  (68)  has  dialyzed  zirconyl  nitrate  solutions,  finding  the  outside 
water  free  from  nitric  acid  after  five  days  and  getting  a  colloidal 
solution  of  the  hydroxide  as  a  hydrosol  which  was  clear  in  trans- 
mitted and  cloudy  in  reflected  light.  The  colloid  was  precipitated  by 
electrolytes.  The  Tsigmondy  gold  number  was  found  to  be  between 
0.046  and  0.09  with  a  mean  of  0.5. 

Rosenheim  and  Frank  could  obtain  no  double  nitrates  with  the 
alkali  nitrates  (610) .  When  ammonia  is  allowed  to  act  upon  zirconyl 
nitrate  (ZrO(N03)2.2H20)  a  white,  crystalline  mass,  scarcely  hygro- 
scopic and  stable  in  the  air,  is  obtained.  The  composition  is  given 
asZrO(N03)2.2H20.2NH3  (405). 

Compounds  with  the  Acids  of  Phosphorus 

On  account  of  the  scant  and  imperfect  references  in  the  literature 
it  is  impossible  to  give  a  systematic  account  of  the  compounds  of  zir- 
conium and  the  zirconyl  radical  with  the  various  acids  of  phosphorus. 
Investigations  of  such  possible  compounds  along  modern  lines  and 
based  on  a  fuller  knowledge  of  their  probable  behavior  are  needed. 


90  ZIRCONIUM  AND  ITS  COMPOUNDS 

Wunder  and  Jeanneret  (828)  have  found  that  metallic  zirconium 
is  readily  dissolved  by  a  hot  solution  of  phosphoric  acid  (Sp.  Gr. 
1.75).  A  clear,  colorless  solution  results  and  whatever  carbon  was 
present  is  left  undissolved.  Further  addition  of  water  causes  no  pre- 
cipitation. No  effort  to  separate  or  determine  the  compound  formed 
was  reported. 

Hautefeuille  and  Margottet  (307)  found  that  zirconium  hydroxide 
was  dissolved  in  phosphoric  acid  heated  to  a  temperature  short  of 
dehydration  and  therefore  probably  in  the  form  of  pyrophosphoric 
acid.  The  amount  dissolved  was  two  parts  in  one  hundred  of  the 
acid.  On  cooling  two  varieties  of  crystals  separated  from  the  fused 
mass.  These  were  described  as  regular  octahedra  and  cubic  octa- 
hedra.  They  had  high  refractive  power  but  showed  no  action  on 
polarized  light.  They  were  not  attacked  by  acids  nor  by  potassium 
bisulphate  but  were  easily  decomposed  by  fusion  with  alkali  car- 
bonates, giving  insoluble  alkali  zirconates  which  could  be  obtained 
free  from  the  phosphoric  acid.  In  this  fusion  the  temperature  was 
kept  as  low  as  possible  and  the  exact  equivalent  of  alkali  carbonate 
used.  This  method  of  separation  was  used  for  the  analysis,  which 
gave  the  empirical  formula  Zr02.P205.  This  may  be  written  ZrP207 
and  the  compound,  therefore,  is  the  pyrophosphate. 

Knop  (400)  fused  zirconia  with  sodium  ammonium  phosphate  at 
a  high  temperature  and  for  a  considerable  time.  The  cooled  mass 
was  leached  with  dilute  hydrochloric  acid.  A  white  powder  was 
left  which  was  clearly  crystalline  under  the  microscope,  the  form  being 
that  of  rectangular  parallelopideds.  They  resembled  the  crystals  of 
sodium  zirconium  phosphate.  The  analyses  are  faulty  but  point  to 
the  same  composition  as  above,  ZrP207.  It  is  by  no  means  assured 
that  these  crystals  did  not  contain  sodium. 

Weibull  (794),  making  use  of  precipitation  methods,  obtained  the 
following  results:  On  addition  of  an  aqueous  solution  of  zirconyl 
chloride  to  an  excess  of  disodium  phosphate  in  solution  a  finely 
divided  white  precipitate  was  formed.  This  was  insoluble  in  weak 
acids  and  in  an  excess  of  the  disodium  phosphate.  It  was  slightly 
soluble  in  hydrochloric  acid,  more  easily  soluble  in  sulphuric  acid. 
When  dried  it  was  insoluble  in  acids.  By  analysis  its  composition 
was  shown  to  be  ZrP207.2H20.  A  similar  result  was  obtained  by 
dropping  a  solution  of  zirconium  sulphate  into  one  of  disodium  pyro- 
phosphate, Na2H2P207,  the  analysis  giving  the  composition  as 
ZrP207.1.5H20.  Another  experiment  in  which  the  solutions  of  zir- 


COMPOUNDS  WITH  ACIDS  OF  NITROGEN  GROUP      91 

conyl  chloride  and  sodium  phosphate  were  simply  mixed  gave  a  basic 
compound,  5Zr02.3P205.9H20.  Still  another  carried  out  in  the  same 
manner  yielded  a  basic  compound  3Zr02 .  2P205 .  5H20,  and  the  same 
result  was  obtained  when  phosphoric  acid  was  used  as  the  precipi- 
tant. Probably  the  zirconyl  chloride  solution  used  had  the  same 
previous  history  as  to  dilution,  time,  and  temperature.  A  somewhat 
similar  result  but  differing  from  the  foregoing  in  the  ratio  of  the  com- 
ponents was  obtained  by  the  independent  investigators,  Hermann 
(319)  and  Paykull  (537),  on  adding  solutions  of  disodium  phosphate 
to  one  of  zirconyl  chloride.  They  obtained  precipitates  whose  com- 
position was  represented  by  the  formula  5Zr02.4P205.8H20.  Such 
uniformity  in  results  is  confirmatory  evidence  that  these  are  not 
accidental  or  indefinite  mixtures  but  are  regularly  formed  when  the 
conditions  are  even  approximately  duplicated. 

The  experiments  which  have  been  detailed,  therefore,  show  that 
when  a  solution  of  the  zirconyl  salt  is  added  to  an  excess  of  a  solu- 
tion of  any  of  the  phosphates  the  result  is  the  formation  of  the 
pyrophosphate.  When,  however,  these  conditions  are  not  observed 
the  result  is  the  formation  of  basic  zirconyl  phosphates  which  vary 
according  to  the  previous  history  of  the  solution  of  the  zirconyl  salt 
or,  in  other  words,  the  extent  to  which  hydrolysis  has  proceeded. 
With  the  exception  of  such  basic  compounds  or  mixtures  as  have  been 
mentioned  above  the  pyrophosphate  is  the  only  zirconium  phosphate 
known.  The  marked  tendency  to  form  this  instead  of  the  other  phos- 
phates is  noteworthy. 

As  to  compounds  with  other  acids  of  phosphorus,  Hauser  and 
Herzfeld  (299)  have  reported  that  on  the  addition  of  sodium  sub- 
phosphate,  Na4P2O6,  in  excess  to  a  slightly  warmed  solution  of  zir- 
conyl nitrate  in  dilute  hydrochloric  acid  a  fine,  crystalline  precipitate 
practically  insoluble  in  dilute  acid  was  formed.  The  composition  of 
this  zirconium  subphosphate  was  given  as  ZrP206.H20,  and  this  on 
ignition  gives  ZrP207.  Thorium  forms  a  similar  compound,  which 
would  have  to  be  borne  in  mind  when  this  reaction  is  used  for  ana- 
lytical purposes. 

These  authors  also  stated  that  when  hypophosphorous  acid  was 
added  to  a  solution  of  zirconyl  nitrate  in  water  there  was  formed  an 
amorphous  precipitate  which  slowly  dissolved  in  an  excess  of  the  pre- 
cipitant. Any  insoluble  portion  due  to  the  presence  of  phosphates 
was  filtered  off.  Electrolytic  experiments  showed  the  zirconium  ions 
as  complex,  migrating  with  the  negative  stream.  On  the  addition  of 


92  ZIRCONIUM  AND  ITS  COMPOUNDS 

alcohol  a  precipitate  consisting  of  fine  crystals  was  formed.  These 
had  strong  refractive  powers  and  exhibited  a  double  polarization. 
The  composition  was  that  of  the  hypophosphite  Zr(H2P02)4.  When 
freshly  precipitated  the  crystals  contained  one  molecule  of  water 
which  was  easily  separated.  They  showed  a  peculiar  light  sensibility. 
By  direct  sunlight  they  were  rapidly  colored  deep  violet.  In  diffuse 
light  this  took  place  only  after  the  expiration  of  a  number  of  weeks. 
No  dissociation  could  be  detected  in  these  colored  crystals  under  the 
microscope. 

Double  Phosphates  with  Alkali  Metals.  Only  those  obtained  with 
potassium  and  sodium  phosphates  are  on  record.  With  potassium  the 
following  compounds  have  been  reported:  Troost  and  Ouvrard  (719) 
found  that  when  zirconia  or  the  phosphate  or  anhydrous  zirconyl 
chloride  were  dissolved  in  fused  potassium  metaphosphate  until  no 
more  was  taken  up  and  the  cooled  mass  then  leached  with  acidulated 
water  to  remove  the  excess  of  potassium  metaphosphate  there  re- 
mained a  double  phosphate  as  a  crystalline  powder,  apparently  rhom- 
bohedric  and  belonging  to  the  hexagonal  system.  These  crystals  acted 
strongly  on  polarized  light  and  had  a  density  of  3.18.  They  were 
not  acted  upon  by  acids  nor  aqua  regia.  The  composition  was 
K20.4Zr02.3P205.  When  fused,  potassium  pyrophosphate  was  used 
as  the  solvent  and  treated  in  the  same  way  a  crystalline  powder  of  hex- 
agonal lamella?  was  left  and  this  also  acted  on  polarized  light.  These 
were  soluble  in  H2S04  but  insoluble  in  HC1  or  HN03.  The  density  was 
3.08  and  the  composition  K2O.Zr02.P205.  On  adding  potassium 
chloride  to  the  above  fusion  to  make  it  more  fusible,  the  same  salt 
was  obtained  and,  in  addition,  another  insoluble  double  phosphate 
forming  small  tetrahedral  crystals,  which  was  not  further  examined. 
Fusion  with  the  orthophosphate  K3P04,  gave  no  definite  results,  but 
when  KC1  was  added  the  same  results  were  obtained  as  with  the  pyro- 
phosphate. When  these  double  phosphates  were  heated  to  a  very  high 
temperature  all  was  volatilized  except  the  zirconia,  which  was  left  in  a 
crystalline  form.  The  density  was  5.73  at  17°. 

Sodium  and  Zirconium  Phosphates.  Knop  (400)  prepared  a 
double  phosphate  of  sodium  and  zirconium  by  fusing  zirconia  with 
sodium  ammonium  phosphate  and  keeping  it  at  a  white  heat  for  two 
hours.  After  leaching  the  cooled  mass  with  dilute  hydrochloric  acid 
and  removing  an  amorphous  portion  there  was  left  a  crystalline  meal 
consisting  of  colorless,  transparent  crystals  in  the  form  of  rectangular 
parallelepipeds  which  acted  on  polarized  light.  These  crystals  have 


COMPOUNDS  WITH  ACIDS  OF  NITROGEN  GROUP      93 

also  been  described  by  Wunder  (825)  as  tetragonal  combinations  of 
prisms  and  basic  pinacoids.  Density  determinations  gave  3.12-3.14. 
They  are  insoluble  in  aqua  regia.  Analysis  showed  their  composi- 
tion to  be  Na20.4Zr02.3P205,  thus  corresponding  with  the  potassium 
compound.  Troost  and  Ouvrard  (719)  using  sodium  metaphosphate 
as  a  flux  with  the  addition  of  a  small  amount  of  sodium  chloride,  ob- 
tained rhombohedral  crystals  having  a  density  of  3.10,  whose  com- 
position was  also  Na20.4Zr02.3P205.  With  sodium  pyrophosphate 
as  a  flux  small  crystals  whose  form  could  not  be  well  determined  were 
obtained.  The  density  was  2.88  and  the  composition  corresponded 
to  the  formula  6Na20.3Zr02.4P205.  These  crystals  acted  slightly  on 
polarized  light,  were  optically  bi-axial,  and  crystallized  in  hexagonal 
lamellae.  When  a  large  amount  of  salt  was  used  in  the  fusion  pris- 
matic crystals,  which  acted  energetically  upon  polarized  light  with 
longitudinal  extinction,  were  obtained.  They  were  soluble  in  acids 
and  had  a  density  of  2.43.  The  analysis  agreed  with  the  formula 
4Na2O.Zr02.2P205. 

Compounds  with  Arsenic  Acid 

When  disodium  arsenate  is  added  to  a  solution  of  Zr(S04)2  a 
white  powder  is  precipitated  in  a  hydrated  condition.  Dried  at  100° 
there  are  two  and  a  half  molecules  of  water,  Paykull  (536) ;  at  110°, 
one  molecule  Kulka  (417).  Analysis  showed  the  composition  to  be 
2Zr02 . As205 . H20  or  2.5H2O.  When  sodium  arsenate  was  added  to 
a  dilute  hydrochloric  acid  solution  of  ZrOF2  a  voluminous  white  pre- 
one  molecule,  Kulka  (417).  Analysis  showed  the  composition  to  be 
3Zr02.2As205.5H20  (794).  Berzelius  (55)  obtained  an  orange-yellow 
precipitate,  which  darkened  on  drying  and  was  not  decomposed  by 
acids,  by  adding  a  solution  of  NaSH,  saturated  with  As2S3,  to  a  solu- 
tion of  a  zirconium  salt.  The  supernatant  liquid  retained  a  yellow 
color.  He  called  the  precipitate  zirconium  sulpharsenite.  He  also 
stated  that  tri-  and  disodium  sulpharsenates  gave  with  zirconium  salts 
citron-yellow  precipitates  which  became  orange-yellow  on  drying  and 
were  not  decomposed  by  acids. 

Compounds  with  Antimonic  Acids 

When  a  cold,  neutral  solution  of  potassium  pyroantimonate  is 
added  to  a  solution  of  Zr(S04)2  a  curdy  white  precipitate  is  formed, 
insoluble  in  water  but  easily  soluble  in  hydrochloric  acid.  The  anal- 


94  ZIRCONIUM  AND  ITS  COMPOUNDS 

ysis    of    the    air-dried    sample    showed    the     composition    to    be 

Zr02.Sb205.7.5H20,  or  a  hydrated  pyroantimonate  ZrSb207  (417). 
i 

Compounds  with  Chromic  Acid 

Weibull  (794)  reported  that  a  precipitate  was  formed  on  adding  a 
solution  of  chromic  acid  to  one  of  zirconyl  chloride,  but  no  details 
were  given  as  to  the  conditions  observed  in  the  experiment  nor  the 
composition  of  the  product.  Haber  (276)  stated  that  this  precipitate 
was  flocculent,  orange-yellow  in  color,  and  difficultly  soluble  in  dilute 
acid;  also  that  the  chromic  acid  could  be  gradually,  though  not  com- 
pletely, leached  out  with  water.  Venable  and  Giles  (748)  made  a 
more  detailed  examination  of  this  reaction  and  the  resulting  product. 
The  use  of  an  alkali  chromate  as  the  precipitant  is  inadvisable  on 
account  of  the  persistent  retention  of  the 'acid  originally  in  combina- 
tion with  the  zirconyl,  thus  rendering  the  product  impure.  Zirconium 
hydroxide,  prepared  in  the  cold,  was  dissolved  in  a  concentrated  solu- 
tion of  chromic  acid.  A  portion  of  this  solution  allowed  to  evaporate 
over  a  dehydrating  agent  in  partial  vacuum  yielded  no  crystals  but 
gave  a  small  amount  of  a  reddish-yellow  precipitate  which  was  prob- 
ably a  mixture  of  chromate  and  bichromate.  When  the  solution  was 
considerably  diluted  and  boiled  there  was  formed  a  yellow  precipitate 
which  was  quite  insoluble  in  water.  This  precipitate  was  granular 
or  possibly  very  finely  crystalline.  The  water  of  hydration  was  for 
the  most  part  lost  on  heating  at  100°  and  completely  lost  below  200°. 
Analyses  of  several  preparations  corresponded  to  the  formula 
Zr305 . 0203  on  the  dry  basis,  or,  when  the  water  present  is  taken  into 
account,  ZrO(OH)2.2ZrOCr04.2H20. 

Compounds  with  Tungstic  Acid 

Kulka  (417)  added  to  a  solution  of  zirconyl  nitrate  in  the  cold 
a  solution  of  ammonium  metatungstate,  obtaining  a  gelatinous  pre- 
cipitate. This  precipitate,  after  boiling,  was  placed  on  a  suction  filter, 
washed  with  hot  water,  and  then  dried.  The  composition,  deduced 
from  the  analysis,  was  5Zr02.9W03.33H20.  By  similar  treatment 
of  a  precipitation  made  by  means  of  sodium  paratungstate  a  substance 
corresponding  to  the  formula  5Zr02.7W03.21H20  was  obtained.  The 
composition  of  these  pecipitates  was  doubtless  determined  by  the 
extent  of  the  hydrolysis  of  the  zirconyl  salt  used.  These  substances 
may  be  considered  zirconium  tungstic  acids. 


COMPOUNDS  WITH  ACIDS  OF  NITROGEN  GROUP     95 

Kulka  also  prepared  a  potassium  salt  by  dissolving  Zr(OH)4  in  a 
boiling  solution  of  potassium  paratungstate.  On  concentration  the 
excess  of  potassium  paratungstate  crystallized  out.  There  formed 
a  crop  of  lengthened  elliptical  crystals,  microscopic  in  size,  which  had 
the  composition  K20 .  Zr02 .  2W03 . 33H20.  No  further  crops  differing 
in  crystal  form  were  obtained  by  him. 

Hallopeau  (280)  used  a  solution  of  potassium  paratungstate 
(5K20.12W03.11H20)  in  which  he  dissolved  Zr(OH)4  by  prolonged 
boiling.  The  solution  was  alkaline.  It  was  filtered  clear  and  crys- 
tals separated  on  standing.  These  were  redissolved  in  boiling  water 
and  re-crystallized.  The  crystals  were  microscopic  and  feebly  active 
optically.  Analysis  showed  them  to  be  potassium  zircono-decitung- 
state,  4K20 .  Zr02 . 10W03 . 15H20.  From  the  mother  liquor  separated 
a  crop  of  very  small  prismatic  crystals  which  acted  with  more  energy 
upon  polarized  light  with  longitudinal  extinction.  These  were  potas- 
sium dizircono-decitungstate,  4K20.2Zr02.10W03.20H20.  Twelve 
molecules  of  this  water  were  lost  on  heating  at  100°.  These  zirconium 
compounds  are  less  stable  than  the  analogous  ones  of  silicon. 

Likewise,  by  dissolving  Zr(OH)4  in  a  solution  of  ammonium  para- 
tungstate and  concentrating  the  solution  over  a  dehydrating  agent 
in  partial  vacuum  to  a  syrupy  consistency,  there  were  obtained  small, 
prismatic  crystals  which  were  strongly  refractive  and  active  to  polar- 
ized light.  They  were  easily  dissolved  in  water  and  purified  by  re- 
crystallization.  Their  composition  was  that  of  ammonium-zircono- 
decitungstate,  3(NHJ2O.ZrO2.10W03.14H20.  Most  metallic  chlo- 
rides, nitrates,  etc.,  gave  insoluble  precipitates  with  these  compounds. 

Berzelius  (58)  reported  his  experiments  on  the  formation  of  zir- 
conium sulpho-tungstate. 

Compounds  with  Molybic  Acids 

Since  zirconium  hydroxide  is  insoluble  in  ammonium  molybdate 
solution,  compounds  can  not  be  obtained  by  methods  used  for  the 
tungstates.  Kulka  (417)  prepared  a  molybdate  by  dropping  a  solu- 
tion of  ammonium  molybdate  into  a  cold  solution  of  Zr(SOJ2  until 
a  permanent  precipitate  was  formed.  The  precipitate  is  gelatinous 
and  can  be  washed  free  from  (NHJ2S04.  It  is  insoluble  in  water 
but  easily  soluble  in  hot  hydrochloric  acid.  The  composition  is 
Zr02.2Mo03.21H20 — zirconium  molybdic  acid. 

Salts  of  a  somewhat  similar  acid  have  been  prepared  by  Pechard 


96  ZIRCONIUM  AND  ITS  COMPOUNDS 

(538) .  The  ammonium  salt  was  formed  by  adding,  in  small  portions, 
ammonium  fluozirconate  to  a  solution  of  ammonium  molybdate.  The 
solution  acquires  a  deeper  and  deeper  yellow  color.  When  this  change 
ceases  the  addition  of  an  excess  of  hydrochloric  acid  causes  the  for- 
mation of  ammonium-zirconium  molybdate.  This  forms  yellow  octahe- 
dral crystals  whose  composition  is  3(NH4)2O.ZrO2.12Mo03.10H20, 
The  potassium  salt  is  prepared  similarly.  In  this  case  the  crystals 
are  brown  and  may  be  several  centimeters  long,  and  effloresce  on 
standing.  The  composition  is  3K2O.Zr02.12Mo03.10H20.  These 
compounds  are  analogous  to  those  of  titanium  and  tin. 

Compound  with  Vanadic  Acid 

A  complex  compound  with  vanadic  acid  has  been  prepared  by 
Rogers  and  Smith  (598).  A  solution  of  ammonium  paratungstate 
was  boiled  for  ten  hours  with  an  excess  of  zirconium  hydroxide.  Then 
ammonium  phosphate  was  added  and  boiled  two  hours;  and  lastly, 
ammonium  metavanadate,  which  had  been  reduced  to  the  hydrate  of 
the  trioxide,  was  added  and  boiled  two  hours.  Crystals  separated 
from  the  concentrated  solution  in  large  black  octahedra.  They  were 
very  soluble  in  water.  Nitric  acid  dropped  on  the  crystals  caused 
decomposition.  The  analysis  showed  the  composition  to  be  (NH4)20 
=  5.35;  Zr02=:0.63;  V203  =  14.28;  P205=:2.49;  W03  =  62.29; 
H  0  =  14.96.  This  substance  was  named  by  the  authors  ammonium- 
zircono-vanadico-phospho-tungstate.  Similar  complexes  have  been 
prepared  for  silicon,  titanium,  tin,  and  thorium. 


Chapter  VII 

Compounds  with  Acids  of  the  Silicon  Group 
Compounds  with  Titanic  Acid 

According  to  Berzelius,  a  precipitate  of  zirconium  titanate  is 
formed  on  mixing  solutions  of  zirconium  and  titanium  chlorides  and 
adding  to  this  a  solution  of  potassium  sulphate.  Details  are  lack- 
ing and  artificially  prepared  titanates  have  not  been  further  inves- 
tigated. A  number  of  the  zirconium  minerals,  however,  carry  appre- 
ciable quantities  of  titanium,  also  niobium  and  tantalum.  In  these 
it  may  be  assumed  that  the  oxides  of  the  elements  named  form  the 
acid  constituents.  Polymignite,  for  instance,  contains  46.30  p.c.  of 
Ti02  combined  with  14.14  p.c.  Zr02,  12.2  p.c.  Fe203,  2.7  p.c.  Mn203; 
4.2  p.c.  CaO,  the  remainder  consisting  of  the  oxides  of  the  rare  earths 
with  traces  of  other  oxides.  Mengite  is  chiefly  Ti02  combined  with 
Zr02  and  Fe203. 

Compounds  with  Silicic  Acid 

Zirconium  Silicate.  The  natural  silicate,  known  as  the  zircon  or 
hyacinth,  is  the  most  abundant  mode  of  occurrence  of  zirconium  and 
also  the  most  widely  distributed.  The  crystal  form  is  chiefly  with 
the  combination  of  faces  [110],  [111],  often  with  a  rhombohedral 
development  and  frequently  thereby  [311].  The  faces  [110]  and 
[111]  are  usually  well  developed.  An  imperfect  cleavage  is  shown 
along  [110]  and  slightly  also  along  [100]  and  [111].  They  have  a 
refractive  action  on  light.  They  are  to  be  classified  as  belonging  to 
the  tetragonal  system  of  the  bipyramidal  class.  The  zircon  is  iso- 
morphous  with  thorite  (ThSiOJ. 

The  crystals  are  usually  opaque  and  of  a  brown-red  color.  Others 
are  transparent  and  variously  colored,  though  some  are  colorless.  The 
opaque  crystals  also  have  a  range  of  colors,  but  these  are  rarer  than 
the  brown-red.  They  vary  in  size  from  microscopic  to  several  inches 
in  length.  The  hyacinth  is  transparent  and  of  a  deep  red  color. 

97 


98  ZIRCONIUM  AND  ITS  COMPOUNDS 

These  and  the  transparent  crystals  are  classed  with  the  precious 
stones. 

The  zircon  is  found  in  igneous  rock  of  various  ages  and  also  in 
the  detritus  from  these.  Though  the  zircon  is  very  resistant  to 
weathering  agencies,  a  number  of  altered  zircons  are  known.  Among 
these  may  be  mentioned  alvite,  anderbergite,  auerbachite,  beccarite, 
cyrtholit,  oerstedtite,  ostranite,  and  tachyaphaltite. 

The  following  analyses  of  the  zircons  (unaltered)  may  be  cited 
as  showing  the  average  composition: 

Analyst  Locality  Zr02  SiOa          Fe,08 

Klaproth  Norway  65.  33.  1. 

Berzelius  Expailly  67.16  33.48 

Damour  North  Carolina  65.30  33.21 

Chandler  Ceylon  66.92  33.40  0.67 

Weatherell  Reading  63.50  34.07  2.02 

Morehead  North  Carolina  62.83  33.98 

A  qualitative  analysis  of  zircon  from  Green  River,  N.  C.,  by  More- 
head  (504)  revealed  the  presence  of  Zr,  Si,  O,  Fe,  Na,  K,  Mg,  Ca, 
Al,  Pb,  Sn,  U,  and  Er.  A  more  exhaustive  analysis  by  Linnemann 
(449)  gave  nineteen  elements  as  present,  namely,  Zr,  Si,  0,  Na,  K, 
Li,  Mg,  Ca,  Al,  Fe,  Mn,  Cu,  Pb,  Sn,  Zn,  U,  Er,  Bi,  and  Co.  Pereira- 
Forjaz  (539)  reported  from  his  electrographic  study  of  Portuguese 
zircons  the  presence  of  Zr,  Si,  0,  Ca,  Al,  Fe,  Th,  Ti,  Mg,  Sn,  Bi,  and 
Cu.  Hannay  (281)  has  reported  traces  of  cerium  and  didymium. 
Thorium  has  been  reported  in  a  zircon  from  Schwalbenberg  as  present 
to  the  amount  of  2.06  p.c.  and  yttrium  as  3.47  p.c.  (821).  The  iron 
content  can  be  considerable,  as  much  as  9  p.c.  having  been  reported 
by  Konig  (406,  407).  Some  of  these  elements  present  doubtless  may 
be  regarded  as  impurities  from  infiltrations.  The  fairly  regular  pres- 
ence of  the  five  group  analogues,  Si,  Ti,  Th,  Sn,  and  Pb,  is,  however, 
noteworthy.  Zirconium  also  shows  many  analogies  to  the  aluminum 
and  iron  which  are  always  present.  The  absorption  spectrum  given 
by  many  zircons  is  ascribed  to  the  uranium  and  rare  earths  present 
(36).  As  uranium  is  said  to  be  always  present,  the  radio-activity 
observed  and  also  the  accompanying  lead  may  be  assigned  to  this 
element.  Zircons  may  be  freed  from  iron  and,  in  some  cases,  opaque 
zircons  may  be  rendered  transparent  by  heating  them  in  an  atmos- 
phere of  carbon  tetradhloride,  carbonyl  chloride,  or  sulphur  chloride. 
Baddeleyite,  the  native  zirconia  ore  from  Brazil,  also  contains 
several  of  the  analogous  elements  of  the  fourth  group.  In  connection 
with  it  is  found  another  natural  zirconium  silicate  which  may  contain 


COMPOUNDS  WITH  ACIDS  OF  THE  SILICON  GROUP       99 

as  much  as  75  p.c.  of  zirconia.  This  would  appear  to  be  a  basic  sili- 
cate. It  differs  from  the  ordinary  zircon  in  its  complete  solubility  in 
dilute  hydrofluoric  acid,  which  leaves  the  zircon  unattacked.  This  is 
called  zirkelite. 

Zircon  is  not  acted  upon  by  dilute  or  concentrated  acids.  Hydro- 
gen fluoride  attacks  it  only  at  high  temperatures.  If  mixed  with 
carbon  and  heated  to  a  high  temperature  it  is  acted  upon  by  fluorine 
and  chlorine.  Its  melting  point  has  been  lately  determined  (762)  as 
2550°.  A  mixture  of  Zr02  and  Si02  in  molecular  proportions  melts 
at  the  same  temperature  (762).  Cussak  (158)  failed  to  melt  it  when 
using  a  Joly  meldometer  and  drew  the  conclusion  that  the  melting 
point  was  1760°  or  higher.  It  is  slowly  taken  up  in  a  fusion  with 
borax,  also  in  microcosmic  salt  (340).  The  fusion  with  potassium 
or  sodium  hydroxide  is  also  difficult  and  imperfect.  The  addition, 
however,  of  moderate  amounts  of  sodium  fluoride  brings  about  a  rapid 
and  complete  fusion. 

The  density  of  the  zircon  ranges  from  4.0  to  4.7;  the  hardness 
from  7  to  8 — therefore  approaching  that  of  the  diamond.  The  formula 
is  ordinarily  written  ZrSi04.  Vegard  (727,  728,  729,  730),  from  his 
study  of  the  crystal  lattice  structure,  reached  the  conclusion  that  the 
formula  should  be  written  Zr02.Si02,  since  the  zirconium  and  silicon 
atoms  were  found  to  be  similarly  placed  in  regard  to  the  oxygen 
atoms. 

Luminescence  of  Zircons.  It  has  long  been  known  that  zircons 
from  certain  localities,  as  Norway  and  Expailly,  phosphoresce  when 
heated  to  the  temperature  of  low  redness.  Some  of  the  zircons  under 
this  treatment  become  colorless  and  transparent;  also,  in  most  cases 
the  density  is  permanently  increased.  A  number  of  investigations 
have  been  made  as  to  the  cause  and  possible  interrelation  of  these 
phenomena.  Damour  (161)  has  shown  that  there  is  slight  and 
often  inappreciable  loss  in  weight  on  heating.  Also,  he  has  pointed 
out  that  the  index  of  refraction  is  changed  as  well  as  the  density,  and 
that  the  increased  density  remains  unchanged  even  when  the  heating 
is  pushed  to  fusion,  except  in  one  or  two  of  the  cases  examined.  He 
suggested  that  it  might  be  a  matter  of  allotropism,  the  action  of  heat 
bringing  about  a  change  into  the  second  allotropic  modification. 
Fizeau  (220)  has  shown  that  heat  causes  a  lasting  expansion  of  form. 
This  would  operate  against  an  increase  of  density  on  heating.  Ex- 
periments by  Stevanovic  (681),  however,  show  that  zircons  having  a 
density  under  4.7  may  have  their  density  raised  to  that  figure.  The 


100  ZIRCONIUM  AND  ITS  COMPOUNDS 

range  of  density  of  the  native  zircons  is  from  4.0  to  4.7.  Where  the 
zircon  has  this  maximum  density  already  it  is  unchanged  on  heating. 
The  heating  of  a  zircon  then  causes  a  slight  loss  of  weight,  which 
may  be  due  to  driving  off  some  of  the  volatile  constituents,  a  change 
of  form,  an  increase  in  density,  and  a  temporary  phosphorescence.  If 
the  heating  is  for  a  brief  period  only,  the  phosphorescence  may  be 
re-induced  by  a  repetition  of  the  heating.  After  a  few  such  re-heat- 
ings the.  zircon  loses  the  power  of  phosphorescing  on  the  application  of 
heat.  In  some  of  the  theories  advanced  to  explain  this  luminescence 
it  has  been  assumed  to  bear  some  relation  to  the  color  of  the  zircon, 
which  may  also  be  lost  on  heating.  According  to  Henneberg  (316) 
the  luminescence  appears  at  a  temperature  below  that  at  which  the 
color  is  lost  or  changed.  The  loss  of  weight  ranges  from  practically 
zero  to  0.45  p.c.  of  the  weight  and  the  change  of  density  from  1,0  to 
2.5  p.c.  A  brown-red  color  is  lost  at  a  temperature  of  about  300°. 
Spezia  (671)  drew  the  conclusion  from  his  experiments  that  this  loss 
was  due  to  the  reduction  of  the  ferric  compounds  present  and  main- 
tained that  heating  in  a  stream  of  oxygen  restored  the  color.  The 
experiments  of  Hermann  (329)  were  more  detailed  and  exhaustive 
and  he  agreed  with  Spezia  that  the  color  is  largely  due  to  iron  in 
different  stages  of  oxidation  and,  in  the  case  of  a  green  color,  to  an 
admixture  of  chromic  oxide.  Doelter  (193)  concluded  from  his  in- 
vestigation that  Spezia  was  wrong  in  assuming  that  iron  confers  the 
color  and  thought  it  to  be  due  to  some  unknown  substance  of  a  col- 
loidal nature.  With  regard  to  density,  he  found  the  green  zircon 
to  have  the  lowest,  and  colorless  zircon  to  have  the  highest.  Green 
and  yellow  zircons,  he  believed,  had  a  different  coloring  matter  from 
the  brown  and  red.  Stevanovic  (681)  stated  that  the  biaxial  green 
zircon  with  a  density  of  4.3  changed  on  heating  into  the  uniaxial,  nor- 
mal zircon  with  a  density  of  4.7.  These  phenomena  attracted  the 
attention  of  several  earlier  investigators  and  led  to  experiments  on 
their  part,  but  the  varying  accounts  as  to  the  properties  and  behavior 
of  zircons  may  in  part  be  explained  by  the  somewhat  wide  variations 
of  the  minerals  coming  from  different  localities,  the  faulty  methods 
of  the  investigators,  and  the  neglect  on  their  part  to  exclude  the  in- 
filtrations of  foreign  matter  which  necessarily  vitiate  their  results. 
Due  precautions  were  taken  by  Doelter  and  other  recent  workers  to 
remove,  as  far  as  possible,  such  matter  as  did  not  form  a  component 
part  of  the  crystals.  The  cathode  luminescence  of  the  zircon  was 
examined  by  Crookes  (154)  and  Pochettino  (558). 


COMPOUNDS  WITH  ACIDS  OF  THE  SILICON  GROUP.  -Jfll 


Further  light  has  been  thrown  on  these  changes  of  color  in  zircons 
by  a  study  of  their  radio-activity  and  the  action  of  radium  emana- 
tions upon  them.  The  radio-activity  of  zircons  is  markedly  greater 
than  that  of  any  other  hard  mineral  occurring  in  igneous  rock.  Fur- 
ther, zircons  contain  hundreds  of  times  more  helium  than  the  average 
rock  with  which  they  are  associated  and  Strutt  (690)  has  made  use 
of  this  fact  as  a  means  of  determining  the  geologic  age  of  the  sur- 
rounding rock.  This  radio-activity  was  in  excess  of  the  uranium  or 
thorium  contents  and  indicated  the  presence  of  an  accumulation  of 
radium.  The  uranium-lead  ratio  has  been  determined  by  Holmes 
(351),  the  percentage  of  uranium  found  being  0.0019  and  of  lead 
0.000085.  Zircons  show  also  a  greater  radio-activity  than  any  other 
mineral  associated  with  monazite.  Zircon  crystals  in  plutonic  rocks 
are  opaque.  Those  in  basalt  and  lavas  are  transparent  and  show 
signs  of  incipient  fusion  (690).  The  transparent  crystals  are  ther- 
moluminescent,  giving  out  a  phosphorescent  glow  and  losing  color 
when  moderately  heated  (200°).  The  glow  is  not  repeated  if  once 
heated  until  it  disappears.  Partial  heatings  bring  out  the  glow  until 
the  property  is  lost.  It  can  be  restored,  and  also  the  color,  by  expo- 
sure for  some  weeks  or  months  to  the  emanations  from  radium  salts. 
Opaque  crystals  are  not  thermoluminescent  nor  made  so  by  exposure 
to  radium.  Nor  are  they  decolorized  by  moderate  heating.  If  kept 
in  melted  basalt  for  twenty-four  hours  they  become  white,  though 
not  transparent,  and  then  on  exposure  to  radium  emanations  they 
become  reddish-brown  like  the  hyacinth  and  thermoluminescent.  This 
treatment,  however,  does  not  make  them  transparent.  It  has  been 
stated  by  Demarcay  (174)  that  zircons  lose  their  color  when  heated 
in  a  stream  of  carbon  tetrachloride.  Splinters  of  opaque  zircons  be- 
come transparent  when  heated  in  such  an  atmosphere  or  in  one  of 
carbonyl  chloride,  these  reagents  removing  the  iron,  aluminum,  and 
probably  some  other  minor  constituents. 

To  the  radio-activity  of  zircons  has  been  assigned  (379)  the  pro- 
duction of  the  pleiochroitic  halos  observed  in  the  enclosing  biotite, 
iolite,  etc.  The  color  of  zircons  in  monazite  resembles  that  given  to 
the  glass  containers  by  radium  salts.  This  color  penetrates  the  crys- 
tals. The  theory  of  Doelter  (194)  that  the  colors  of  zircons  may  be 
due  to  some  element  in  a  colloidal  state  is  in  harmony  with  many 
of  the  known  facts  and  receives  support  from  the  behavior  toward 
radium  emanations  (490) .  The  separation  of  the  finely-divided,  col- 
loidal metal  through  the  action  of  the  rays  is  a  possibility  and  it  is 


402   0- ;;-.,<  ZIRCONIUM  AND  ITS  COMPOUNDS 


well  known  that  the  colorings  given  by  a  metal  in  this  state  may  be 
greatly  varied.  It  must  be  noted  that  not  all  zircons  are  affected  by 
radium.  Brauns  (100)  found  that  originally  colorless  specimens  ex- 
amined by  him  could  not  be  colored.  Grengg  (260)  believed  that  the 
finely-divided  iron  oxide  surrounding  zircon  crystals  in  porphyries, 
which  resembles  the  halos  often  surrounding  zircon  enclosed  in  biotite, 
was  due  to  the  decomposition  of  iron-bearing  solutions  circulating 
through  pore  spaces  of  the  ground  mass  by  emanations  from  zircon 
crystals. 

As  an  accompaniment  of  radio-activity  helium  is  found  in  zir- 
cons, euxenite  (556),  malacone  (391),  baddeleyite  (9),  and  other  zir- 
conium minerals.  Only  20  p.c.  of  the  helium  in  malacone  (whose 
radio-activity  is  very  slight)  could  be  attributed  to  the  uranium  pres- 
ent. The  remaining  80  p.c.  was  due  to  something  else,  possibly 
radium,  according  to  Kitchin  and  Winterson  (391).  On  decomposing 
the  mineral  and  treating  it  to  separate  the  zirconia  they  found  that 
the  activity  remained  with  the  zirconia  and  insoluble  material.  Gum- 
ming (155)  varied  the  treatment  and  found  the  soluble  portion  active. 
According 'to  his  treatment,  this  should  have  contained  the  radium. 
Kitchin  and  others  have  found  that  the  helium  in  malacone  was 
accompanied  by  argon,  and  Antropoff  (9)  detected  argon  in  a  zir- 
conium mineral  from  Brazil.  These  anomalous  observations  have  not 
been  refuted  nor  any  explanation  offered.  The  same  may  be  said  of 
the  observation  by  Ramsay  and  Usher  (581)  that  a  solution  of  zir- 
conyl  nitrate  yielded  carbon  dioxide  and  carbon  monoxide  under  the 
influence  of  radium  emanations,  as  did  solutions  of  the  analogues 
-  Si,  Ti,  Th,  and  Pb. 

Artificial  Zircons.  Deville  and  Caron  (183)  by  passing  at  a  high 
temperature  silicon  fluoride  over  zirconia  or,  reversing  this,  zirconium 
fluoride  over  quartz,  obtained  small  octahedral  crystals,  transparent, 
brilliant,  and  having  approximately  the  hardness  and  density  of  zir- 
cons. Hautefeuille  and  Margottet  (306)  by  fusing  a  mixture  of  zir- 
conia and  silica  in  glacial  phosphoric  acid  prepared  a  zirconium  sili- 
cate. Hautefeuille  and  Perrey  (309)  on  heating  for  a  month  two  parts 
of  zirconia  and  one  part  of  silica  with  lithium  dimolybdate  to  a  tem- 
perature of  700°-1000°  obtained  ditetragonal,  bipyramidal  crystals 
having  a  density  of  4.6.  The  crystal  combination  was  [110],  [HI]. 
Chrustschoff  (140)  heated  a  mixture  of  the  two  hydroxides  Si(OH)4 
and  Zr(OH)4  in  a  closed  platinum  crucible  which  was  enclosed  in  a 
steel  block  for  two  hours  at  a  red  heat,  thus  securing  a  high  pressure 


COMPOUNDS  WITH  ACIDS  OF  THE  SILICON  GROUP      103 

in  addition  to  the  heat.     The  crystals  were  well-formed  and  up  to 
0.18  mm.  in  length.    The  density  was  4.45. 

Natural  Double  Silicates.  Ordinary  zircon  is  probably  a  mixture 
of  zirconium  silicate  with  small  amounts  of  various  double  silicates. 
Certain  other  minerals  are  regarded  as  distinctively  double  silicates. 

Catapleiite  (H2(Na2.Ca)ZrSi3O11).  Hardness  6;  Sp.  Gr.  2.8; 
monoclinic  prismatic;  cleavage  perfect.  On  heating  the  crystals  be- 
come uniaxial  and  go  over  into  the  hexagonal. 

Elpidite  (Na2Si2O5.Zr(Si205)2).  Sp.  Gr.  2.5-2.6;  rhombic  pris- 
matic. 

Eudialyte  (Na13(CaFe)6(SiZr)20052Cl).  Groth  regards  the  chlo- 
rine as  due  to  some  small  admixture,  as  sodalite,  and  assigns  the  for- 
mula Na20.2(CaFe)0.6(SiZr)02. 

Lovenite  (Ca.Fe.Mn.Na.ZrOF.  (Si03)2).  Monoclinic;  hardness 
6;  Sp.  Gr.  3.5. 

Wohlerite  (Na7Ca10Fe3Zr3Si10042F3) .  This  may  also  be  men- 
tioned. 

Artificial  Silicates.  A.  Potassium  zirconium  silicate  (K2O.ZrO2.Si02) . 
This  is  formed  by  melting  together  at  a  bright  red  heat  one  part  of 
zircon  .  and  four  parts  of  potassium  carbonate  for  fifteen  minutes. 
If  the  heating  is  prolonged  potassium  silicate  and  crystalline  zirconia 
are  the  products  according  to  Ouvrard  (531).  This  double  silicate 
crystallizes  in  rhombic  prisms  (224).  These  are  acted  upon  by  hydro- 
fluoric acid  and  ammonium  fluoride  (531). 

B.  (K2O.Zr02.2Si02).  One  part  of  pulverized  zircon  with  two 
to  four  parts  of  caustic  potash  are  heated  in  a  silver  crucible.  The 
mass  is  leached  with  cold  water,  leaving  the  double  silicate  as  a 
finely-divided  powder  (138,  46).  The  complete  removal  of  the  silica 
by  prolonged  heating  with  potassium  carbonate  was  confirmed  by 
Knop  (400) .  When  the  fused  mass  was  leached  with  water  potassium 
silicate  was  dissolved  out  and  potassium  zirconate  was  left.  Melliss 
(479)  by  a  similar  fusion  obtained  a  microscopic,  crystalline  residue 
which  on  analysis  proved  to  have  the  composition  K20 .  Zr02 .  2Si02. 
The  density  was  2.79. 

Sodium  Zirconium  Silicate  (Na20.8Zr02.Si02.llH20).  This 
was  prepared  by  Melliss  (479)  by  the  method  used  for  the  potassium 
compound,  removing  all  soluble  matter  by  leaching  with  water.  The 
crystals  were  microscopically  small,  transparent,  hexagonal  prisms 
and  had  a  density  of  3.53.  The  water  of  hydration  was  lost  at  low 
red  heat  without  indication  of  further  decomposition.  Sulphuric  acid 


104  ZIRCONIUM  AND  ITS  COMPOUNDS 

decomposed  the  crystals.  Another  sodium  zirconium  silicate  with  the 
composition  Na20 .  Zr02 .  Si02  was  obtained  by  Gibbs  (244)  by  fusing 
one  part  of  zircon  with  four  parts  of  sodium  carbonate  and  leaching 
the  residue  by  repeated  boiling  with  a  concentrated  solution  of  sodium 
carbonate.  The  granular  white  powder  which  was  left  was  washed 
with  lukewarm  water  without  decomposition.  Bourgeois  (94)  added 
silica  to  powdered  zircon  and  kept  the  mixture  at  red  heat  for  twenty- 
four  hours  with  a  small  amount  of  melted  sodium  carbonate.  He 
found  that  a  considerable  excess  of  sodium  carbonate  decomposed  the 
salt.  He  determined  the  crystalline  form  as  rhombic  prisms,  0.5  mm. 
broad  and  several  mm.  long.  The  facial  combination  was  of  [110] 
and  [010]  with  angles  of  almost  exactly  60°  without  end  planes. 
The  extinction  was  parallel  and  there  was  double  refraction.  The 
powder  obtained  by  Gibbs  (244)  was  decomposed  by  hot  water  and 
hydrochloric  acid,  and  formed  a  jelly  of  silicic  acid.  The  crystals 
obtained  by  Bourgeois  were  soluble  in  concentrated  acids.  There  is 
doubt  as  to  the  formation  of  double  silicates  by  these  methods.  Ac- 
cording to  Scheerer  (638)  and  others,  only  the  zirconates  are  formed 
in  this  way. 

Calcium  Zirconium  Silicate.  Berthier  (46)  made  various  trials 
at  fusing  zircon,  quartz,  and  marble  in  carbon  crucibles.  The  propor- 
tions were  varied  and  some  of  the  products  were  glassy,  some  enamel- 
like,  and  some  dull  and  stonelike.  The  extent  of  fusion  differed,  as 
did  also  that  of  the  homogeneity  of  the  product.  No  definite  com- 
pounds were  reported.  As  has  been  stated,  calcium  is  found  in  many 
natural  zircons  and  these  may  contain  small  amounts  of  calcium 
zirconium  silicate. 

Berthier  (46)  also  reported  the  results  of  his  experiments  in  fusing 
zircon  and  litharge  together.  Two  experiments  were  carried  out  on 
a  small  scale.  The  first  yielded  a  translucent  yellow  mass,  which  on 
analysis  gave  Si,  0.097;  Zr,  0.19;  and  PbO,  0.71.  The  second  was  semi- 
translucent  and  not  homogeneous,  showing  partly  olive  and  partly 
green  coloration.  The  analysis  gave  Si,  0.15;  Zr,  0.30;  and  PbO,  0.55. 
There  is  no  proof  of  a  definite  lead  zirconium  silicate  but  some  evi- 
dence that  in  some  form  the  lead  enters  into  the  combination. 


Chapter  VIII 
Zirconic  Acid  and  the  Zirconates 

It  would  seem  necessary  to  repeat  here  some  facts  already  noted 
under  the  zirconium  hydroxides.  Normal  zirconium  hydroxide  is 
readily  dehydrated  with  the  loss  of  one  molecule  of  water: 
Zr(OH)4  =  ZrO(OH)2  +  H20.  The  change  takes  place  in  the 
presence  of  water  on  standing  and  is  accelerated  by  heating.  The 
resulting  zirconyl  hydroxide,  ZrO(OH)2,  is  amphoteric,  reacting  with 
acids  to  form  salts,  as  ZrO(OH)2  +  2HC1  =  ZrOCL,  +  2H20.  It 
reacts  with  bases  to  form  salts  of  an  acid,  H2Zr03,  or  zirconic  acid. 
Analogous  acids  are  H2Si03,  H2Ti03,  and  H2Sn03.  Whether  a  meta- 
zirconic  acid  may  be  formed  also  has  not  been  definitely  settled. 
Van  Bemmelen  (34)  has  adduced  arguments  in  favor  of  the  existence 
of  such  an  acid.  Complex  compounds,  which  have  been  called  poly- 
zirconates  and  which  may  correspond  to  the  polysilicates,  are  known. 
The  hydroxide,  ZrO(OH)2  or  Zr02.H20,  has  been  prepared  by  Ruer 
(619)  and  others  by  carefully  drying  the  hydroxide  (precipitated  from 
either  cold  or  hot  solutions)  at  100°,  and  by  Van  Bemmelen  (34)  by 
drying  at  140°.  The  last  molecule  of  water  is  practically  removed  at 
300°,  though  it  is  partly  lost  at  a  somewhat  lower  temperature.  The 
hydroxide,  if  dried  below  200°,  may  be  rehydrated,  but  if  heated  above 
that  temperature  rehydration  is  difficult  and  imperfect.  If  the  tem- 
perature is  raised  rapidly  to  300°  while  as  much  as  one-third  or  more 
of  this  last  molecule  of  water  is  still  present,  sudden  dissociation 
takes  place  with  the  evolution  of  heat  accompanied  by  light,  and 
hence  the  loss  of  potential  energy.  The  hydroxide  ZrO(OH)2  forms 
a  hydrogel  which  may  be  obtained  in  the  colloidal  state.  Observers 
have  reported  the  radical  ZrO  as  migrating  with  either  the  positive  or 
negative  stream. 

Zirconates.  Zirconic  acid  combines  with  strong  bases  to  form  com- 
pounds which  are  insoluble  in  water  and  are  decomposed  by  acids. 
The  slight  solubility  of  zirconyl  hydroxide  in  solutions  of  strong  bases, 
as  the  caustic  alkalies,  practically  limits  the  preparation  of  these 
compounds  to  fusion  methods.  The  fact  that  when  zirconium  hydrox- 

105 


106  ZIRCONIUM  AND  ITS  COMPOUNDS 

ide  is  precipitated  by  an  alkaline  hydroxide  some  of  the  latter  is 
persistently  retained  has  been  looked  upon  as  an  indication  that  a 
compound  has  been  formed.  The  alkali,  however,  can  be  removed 
by  thorough  washing  and  is  doubtless  merely  adsorbed  by  the  col- 
loidal hydroxide.  There  is  similar  adsorption  of  acids,  salts,  etc. 
Some  of  the  products  of  the  fusion  methods  have  been  obtained  in  a 
crystalline  form,  others  as  powders  only.  The  difficulty  of  deciding 
when  a  fusion  reaction  is  complete  leaves  it  uncertain  at  times  as  to 
whether  unattacked  zirconia  is  present,  and  no  entirely  reliable  method 
for  its  separation  has  been  used.  The  usual  method  is  to  wash  free 
from  the  excess  of  base  and  then  decompose  and  dissolve  the  zir- 
conate  with  dilute  acid.  Discordant  results,  which  seem  to  be  due 
to  the  temperature  or  length  of  fusion,  have  been  reported.  It  is 
noteworthy  that  experiments  with  the  alkali  bases  show  a  wide  varia- 
tion and  a  tendency  to  form  polyzirconates,  while  those  with  the 
alkaline  earths  are  quite  uniform,  giving  normal  salts  of  zirconic 
acid. 

Sodium  Zirconates.  When  powdered  zircon  is  heated  for  a  con- 
siderable time  at  a  high  temperature  with  sodium  carbonate  and  the 
resulting  fused  mass,  after  cooling,  is  thoroughly  leached  with  water 
there  is  left,  according  to  Knop  (400),  a  crystalline  sodium  zirconate 
which  is  decomposed  by  hydrochloric  acid.  Ouvrard  (531)  stated 
that  on  using  the  same  method  he  obtained  only  crystallized  zirconia. 
If  the  temperature  used  by  Ouvrard  were  high  enough  to  volatilize  the 
alkali  this  discrepancy  might  be  explained,  or  the  insolubility  of  the 
residue  in  water  may  have  been  considered  sufficient  proof  that  only 
zirconia  was  present.  Earlier  observations  led  to  the  belief  that  the 
zirconates  were  soluble  and  this  error  was  repeated  in  books  of  ref- 
erence. 

Hjortdahl  (342)  attempted  to  determine  the  formation  of  sodium 
zirconates  and  their  composition  by  heating  together  zirconia  and 
sodium  carbonate  and  measuring  the  carbon  dioxide  given  off.  Thus, 
when  these  two  in  approximately  molecular  proportions  were  kept  at 
a  dark  red  heat  for  nine  hours  all  of  the  carbon  dioxide  was  liberated 
and  there  was  left  a  crystalline  mass  which  was  hygroscopic  and  on 
treatment  with  water  yielded  sodium  hydroxide  and  an  amorphous 
mass.  From  the  carbon  dioxide  lost  he  concluded  that  a  compound, 
Na2O.Zr02,  had  been  formed,  although  he  also  heated  sodium  car- 
bonate by  itself  and  measured  the  carbon  dioxide  lost.  The  fusion 
was  likewise  repeated  with  powdered  zircon  and  the  same  material 


ZIRCON  1C  ACID  AND  ZIRCONATES  107 

by  Scheerer  (638)  and  Hermann  (319),  each  concluding  that  the 
material  left  after  leaching  with  water  was  sodium  zirconate. 

Venable  and  Clarke  (747)  found  that  when  zirconia  was  added 
to  a  clear  melt  of  sodium  carbonate  it  sank  to  the  bottom  and  re- 
mained apparently  unattacked  for  hours.  In  a  number  of  experi- 
ments it  was  found  that  90  p.c.  and  over  of  the  zirconia  was  unaltered. 
After  thorough  leaching  with  water  the  mass  was  treated  with  dilute 
hydrochloric  acid  and  the  proportions  of  zirconia  and  soda  in  the 
solution  determined.  In  two  experiments  the  ratio  was  2Na20 .  3Zr02. 
In  a  third,  where  the  heating  was  twice  as  long,  the  ratio  was  approxi- 
mately 3Na20.2Zr02.  When  sodium  hydroxide  was  substituted  for 
the  carbonate  a  much  larger  amount  of  the  zirconia  entered  into  the 
reaction  (40-60  p.c.).  The  ratio  of  Na20  to  Zr02  in  the  hydrochloric 
acid  solution  was  only  from  6.7  to  7.8  Na20  to  93.3-92.2  Zr02. 

A  so-called  sodium  perzirconate  has  been  prepared  by  Pissarjewski 
(555)  by  mixing  two  grams  of  freshly  prepared  hydrated  zirconium 
trioxide  with  200  c.c.  of  hydrogen  peroxide  solution  (2  p.c.)  and 
16  c.c.  of  sodium  hydroxide  solution  (19.5  p.c.).  On  the  addition  of 
double  the  volume  of  alcohol  an  emulsion  was  first  formed  and  then 
a  flocculent  precipitate.  This  was  separated,  dissolved  in  water  at 
0°,  more  hydrogen  peroxide  added  with  a  few  c.c.  of  sodium  hydroxide, 
and  then  about  three-fourths  the  volume  of  alcohol.  The  precipitate 
was  washed  with  alcohol  and  ether  and  became  a  loose  powder  which 
was  partially  dried  over  dehydrating  agents,  washed  again  with 
alcohol  and  ether,  and  dried  between  filter  paper  and  analyzed.  This 
substance  liberated  hydrogen  peroxide  when  treated  with  dilute  sul- 
phuric acid,  and  ozone  and  oxygen  with  concentrated  sulphuric  acid. 
The  composition  calculated  from  the  analysis  was  Na4Zr2011.9H20. 
It  is  difficult  to  classify  this  substance  and  the  similarly  prepared 
E^ZrAi-BH.O. 

Potassium  Zirconates.  It  is  not  practicable  to  prepare  potassium 
zirconate  by  fusing  zirconia  in  potassium  carbonate  because  of  its 
very  slight  solubility  in  that  substance.  Venable  and  Clarke  (747) 
found  that  only  0.5  p.c.  was  dissolved  after  ten  hours'  heating.  When 
potassium  hydroxide  was  used  from  45-75  p.c.  was  taken  up,  forming 
a  compound  which  was  insoluble  in  water  but  soluble  in  dilute  acid. 
The  composition  varied  when  simply  leached  with  water  and  the 
zirconate  then  taken  up  with  dilute  hydrochloric  acid,  indicating, 
perhaps,  a  partial  decomposition  of  the  zirconate.  When  dilute  acetic 
acid  was  substituted  for  the  leach  water  a  substance  was  left  which 


108  ZIRCONIUM  AND  ITS  COMPOUNDS 

had  the  approximate  composition  K20 .  3Zr02.  This  agreed  with  some 
of  the  results  of  Hjortdahl  (342).  It  may  be  called  a  polyzirconate. 

Potassium  perzirconate  (K4Zr20±1.9H20)  has  been  prepared  by 
Pissarjewski  (555)  and  shows  the  same  properties  as  the  sodium  com- 
pound. 

Lithium  Zirconate.  When  lithium  chloride  is  fused  for  some 
hours  with  zirconia  or  powdered  zircon  and  the  mass  extracted  with 
water,  prismatic  crystals  with  longitudinal  extinction  are  left.  These 
are  soluble  in  acids.  The  composition  is  Li2O.Zr02  or  Li2Zr03  (531). 
The  mass  must  be  kept  at  a  high  temperature,  as  ordinary  fusion 
shows  little  action  (747).  Fusion  with  lithium  carbonate  gives  a 
strong  evolution  of  carbon  dioxide  and  zirconia  crystallizes  out  of 
the  melt. 

Lithium  Perzirconate.  This  substance  was  prepared  (531)  by 
fusing  zirconia  in  lithium  hydroxide  and  leaching  the  melt  with  dilute 
acetic  acid.  It  had  the  composition  Li20.2ZrO2  or  Li2Zr205. 

Magnesium  Zirconate.  When  a  mixture  of  silica  and  zirconia  is 
fused  with  magnesium  chloride  in  a  platinum  crucible  whose  bottom 
is  covered  with  ammonium  chloride  and  the  melt  is  raised  quickly  to 
a  white  heat  and  kept  at  that  temperature  for  an  hour  (some  of  the 
magnesium  chloride  volatilizing  and  hence  necessitating  the  use  of 
an  excess),  a  mixture  of  octahedral  and  prismatic  crystals  which  can 
not  be  well  separated  is  obtained.  The  prismatic  crystals  are  re- 
ported as  having  the  composition  MgO.Zr02  (342).  By  heating  a 
mixture  of  four  parts  of  magnesium  oxide  and  one  part  of  zirconia 
and  leaching  the  product  with  dilute  acetic  acid  a  crystalline  salt  with 
the  same  composition,  MgO.Zr02  or  MgZr03  (747),  is  prepared. 

Calcium  Zirconate.  Hjortdahl  (343)  reported  an  acid  calcium 
zirconate  which  he  prepared  by  heating  powdered  zircon  or  a  mixture 
of  silica  and  zirconia  with  an  excess  of  calcium  chloride  for  five  or  six 
hours  at  a  bright  red  heat  and  leaching  the  product  with  dilute  hydro- 
chloric acid.  It  was  described  as  a  brilliant  crystalline  powder.  The 
normal  zirconate  was  prepared  by  Ouvrard  (532)  by  heating  zirconia 
in  melted  calcium  chloride  for  20-30  hours.  The  product  was  leached 
with  water  and  a  crystalline  substance  having  the  composition 
CaO.Zr02  was  left.  According  to  Venable  and  Clarke  (747)  this 
reaction  takes  place  only  after  calcium  oxide  has  been  formed.  They 
heated  zirconia  for  many  hours  with  calcium  oxide  and  leached  the 
product  with  dilute  acetic  acid.  The  crystals  obtained  (532)  had  a 
strong  action  upon  polarized  light  and  were  apparently  isomorphous 


ZIRCONIC  ACID  AND  ZIRCONATES  109 

with  calcium  stannate  and  calcium  titanate.  The  compound  is  the 
normal  calcium  zirconate,  CaZr03. 

Strontium  Zirconate.  Ouvrard  (532)  prepared  this  compound  by 
fusing  zirconia  with  strontium  chloride.  The  reaction  was  brought 
about  with  greater  difficulty  than  in  the  case  of  calcium  zirconate. 
The  crystals  are  similar  to  those  of  calcium  zirconate.  Venable  and 
Clarke  (747)  fused  zirconia  with  strontium  oxide  and  leached  the 
mass  with  dilute  acetic  acid.  Both  found  the  composition  to  be 
SrO.Zr02  or  SrZr03. 

Barium  Zirconate.  Ouvrard  (532)  obtained  opaque  crystals  by 
fusing  zirconia  with  barium  chloride  (difficult).  Venable  and  Clarke 
(747)  found  that  there  was  vigorous  reaction  when  zirconia  was  fused 
with  barium  hydroxide.  The  product  was  leached  with  dilute  acetic 
acid.  It  was  crystalline.  The  composition  was  BaO.ZrO2  or  BaZrO3. 


Chapter  IX 

Organic  Compounds 
Compounds  with  Organic  Acids 

Carbonic  Acid.  It  has  been  stated  by  early  investigators  that 
moist,  gelatinous  zirconyl  hydroxide  readily  absorbs  carbon  dioxide 
from  the  air  (43,  537).  If  the  hydroxide  is  heated  to  100°-150°  in  a 
stream  of  carbon  dioxide  for  twenty-five  to  thirty  hours  the  amount 
absorbed  may  exceed  16  p.c.;  if  suspended  in  water,  as  much  as  7  p.c. 
may  be  taken  up.  This  absorbed  carbon  dioxide  is  given  off  by  the 
dried  substance  in  a  current  of  air,  as  much  as  30  p.c.  being  lost  in 
this  way  and  the  remainder  on  heating  (743).  When  solutions  of 
alkali  carbonates  are  added  to  solutions  of  zirconyl  salts,  white  floc- 
culent  precipitates  soluble  in  an  excess  of  the  precipitant  are  formed. 
Boiling  water  poured  on  these  precipitates  causes  the  evolution  of 
carbon  dioxide  with  foaming.  On  being  washed  with  cold  water  and 
dried  over  sulphuric  acid  the  composition  of  such  a  precipitate  in  one 
analysis  made  was  3Zr02 .  Co2 .  6H20  (319).  The  solubility  in  an 
excess  of  alkali  carbonate  has  been  regarded  as  proof  of  the  formation 
of  double  carbonates.  It  is  possible  that  basic  zirconyl  carbonates 
are  formed  by  some  of  these  methods,  but  there  is  no  evidence  of  the 
preparation  of  a  normal  zirconyl  carbonate.  Whatever  compound  is 
formed  is  very  unstable,  as  is  to  be  expected  with  so  weak  an  acid. 

Formic  Acid.  The  addition  of  formic  acid  or  an  alkali  formate 
to  a  solution  of  a  zirconyl  salt  gives  a  precipitate  which  is  soluble 
in  an  excess  of  the  formate.  An  analysis  of  such  a  precipitate  yielded 
Zr02  76.35  and  HC02H  19.0  (466) .  When  zirconium  tetrachloride  is 
dissolved  in  anhydrous  formic  acid  all  of  the  chlorine  is  liberated  as 
hydrogen  chloride  and  a  crystalline  crust,  which  is  zirconium  formate 
(Zr(HC02)4),  is  obtained  (611). 

Acetic  Acid.  Only  insignificant  amounts  of  zirconyl  hydroxide 
are  dissolved  by  either  hot  or  cold  acetic  acid,  even  when  glacial  acetic 
acid  is  used  (466,  743) .  The  evaporation  of  such  a  solution  leaves  an 
amorphous  powder  which  is  soluble  in  water  or  alcohol  (395,  722). 
This  deposit  has  'been  described  by  Berzelius  as  being  very  hygro- 

110 


ORGANIC  COMPOUNDS  111 

scopic,  and  also  as  being  gummy,  Mandl  (446).  It  is  manifest  that 
the  method  is  inapplicable  for  the  preparation  of  a  definite  compound. 
When  sodium  acetate  is  added  to  a  neutralized  solution  of  zirconyl 
chloride  and  the  whole  heated  the  zirconium  is  completely  precipitated 
as  a  voluminous,  flocculent  basic  acetate.  This  is  soluble  in  warmed 
glacial  acetic  acid  and  the  evaporation  of  this  solution  leaves  a  brittle, 
gumlike  mass  (276) .  The  re-solution  of  such  a  basic  acetate  in  acetic 
acid  does  not  yield  a  neutral  acetate.  The  addition  of  acetic  acid  to 
a  solution  of  a  zirconyl  salt  causes  an  immediate  precipitate  which  is 
redissolved  by  more  acid  (446). 

Zirconium  Acetate  (Zr(C2H302)4).  Rosenheim  and  Hertzmann 
(611)  prepared  this  salt  by  dissolving  zirconium  tetrachloride  in  boil- 
ing anhydrous  acetic  acid.  After  driving  off  the  hydrochloric  acid  by 
heating  the  salt  separated  on  cooling  as  microscopic  prisms,  easily 
soluble  in  water  of  alcohol  but  insoluble  in  ether.  It  is  not  very 
stable  in  air,  losing  acetic  acid.  The  aqueous  solution  is  quickly 
hydrolyzed. 

The  acetate  is  more  quickly  and  completely  hydrolyzed  at  a  lower 
temperature  than  the  salts  of  mineral  acids.  The  hydrolysis  was 
measured  by  the  relative  conductivity  method  and  calculated  in  recip- 
rocal ohms.  The  temperature  at  which  the  measurements  were  made 
was  25°  (611). 

Time  Elapsed 

5Min.         25Min.        45  Min.        18  Hrs.        23  Hrs.        41  Hrs. 
284.2  X  10-6  289.  X  10  6  291.  X  1Q-6310.  X  10'6  310.  X  10'6  310.  X  10'6 
Specific    conductivity    of   the    equivalent    of    acetic    acid    at   25°  = 
289.  X  10-6. 

The  acetate  lends  itself  especially  to  preparing  the  colloidal  hy- 
droxide for  mordanting  and  similar  purposes. 

Zirconyl  Acetate  (ZrO(C2H3O2)2).  This  is  formed  when  the  nor- 
mal acetate  is  allowed  to  stand  for  a  number  of  days  over  sulphuric 
acid.  The  normal  zirconyl  acetate  is  stable  in  dry  air  and  is  soluble 
in  water  or  alcohol.  In  moist  air  it  is  hydrolyzed,  giving  insoluble 
basic  products. 

The  chloracetic  acids,  butyric  acid,  propionic  acid,  etc.,  show  a 
behavior  analogous  to  that  of  acetic  acid. 

Citric  Acid.  Harris  (286)  reported  the  formation  of  a  double 
citrate  of  zirconium  and  ammonium  by  the  addition  of  ammonium 
citrate  to  a  solution  of  zirconyl  chloride.  There  was  formed  a  white, 


112  ZIRCONIUM  AND  ITS  COMPOUNDS 

curdy  precipitate  which  was  washed  and  dried  at  120°.  It  was 
very  deliquescent.  The  analysis  corresponded  to  the  formula 
Zr2.C6H507.(NH4)3. 

Oxalic  Acid.  Oxalic  acid  is  the  best  solvent  for  zirconyl  hydroxide 
among  the  organic  acids,  approaching  the  mineral  acids  in  this  respect 
(681).  Solutions  of  zirconyl  salts  are  precipitated  by  oxalic  acid  or 
ammonium  oxalate,  giving  a  gelatinous  or  flocculent  precipitate  which 
is  nearly  insoluble  in  water  or  dilute  oxalic  acid  (202) .  Zirconyl  sul- 
phate presents  some  anomalies  in  this  regard.  This  has  been  investi- 
gated by  Ruer  (617)  and  explained  on  the  hypothesis  of  the  forma- 
tion of  a  zirconium-sulphuric  acid,  a  supposition  not  accepted  by  later 
investigators.  The  precipitate  formed  with  oxalic  acid  carries  prac- 
tically all  of  the  zirconium.  It  was  found  by  Venable  and  Basker- 
ville  (741)  to  be  basic  and  to  show  a  variable  composition.  It  was 
nearly  insoluble  in  dilute  acids.  Paykull  (536)  reported  the  prepara- 
tion of  an  amorphous  zirconyl  oxalate,  ZrOC204,  and  one  with  two 
molecules  of  water,  ZrOC204.2H20.  Rosenheim  and  Frank  (610), 
on  adding  a  solution  of  oxalic  acid  to  one  of  a  zirconyl  salt,  obtained 
a  gelatinous  precipitate  which  settled  poorly  and  was  filtered  with 
difficulty.  The  addition  of  a  solution  of  NaC2H302  caused  the  pre- 
cipitate to  settle  readily,  and  it  could  be  washed  and  filtered  without 
difficulty.  The  air-dried  precipitate  was  insoluble  in  cold  water  but 
was  hydrolyzed  by  hot  water.  The  composition  was  ZrOC204.4H20. 
When  a  boiling  solution  of  oxalic  acid  was  saturated  with  zirconyl 
hydroxide  and  the  solution  concentrated  over  H2SO4  mixtures  of  large, 
clear,  prismatic  crystals  of  the  oxalate  and  needlelike  crystals  of 
oxalic  acid  were  obtained.  These  were  separated  mechanically 
and  the  oxalate  analyzed.  The  formula  given  (610),  namely, 
ZrOH(C204)3.7H20,  presents  many  difficulties.  The  compound  is 
probably  identical  with  that  obtained  by  Venable  and  Baskerville 
(742)  by  analysis  of  the  one  formed  when  the  precipitated  oxalate  is 
dissolved  in  a  solution  of  oxalic  acid  to  which  some  hydrochloric  acid 
has  been  added.  The  analyses  made  by  these  authors  gave  the 
formula  Zr(C204)2.H2C204.7  (or  8)  H20.  The  salt  forms  fine,  pris- 
matic crystals. 

An  ammonium  zirconium  oxalate  (2(NH4)2C204.Zr(C204)2)  has 
been  reported  by  several  investigators:  Water- free  (697),  4  molecules 
H20  (536) ,  6  molecules  H20  (440) .  It  can  be  prepared  by  dissolving 
zirconyl  hydroxide  in  an  excess  of  oxalic  acid  and  nearly  neutralizing 
with  ammonia.  Crystals  form  from  the  solution  (742).  These  crys- 


ORGANIC  COMPOUNDS  113 

tals  also  form  when  ammonium  oxalate  is  added  to  the  oxalic  acid 
solution  of  the  hydroxide  which  should  contain  free  acid  (537) .  These 
crystals  have  been  described  as  octahedra  and  as  small  monoclinic 
crystals.  They  dissolve  in  either  cold  or  hot  water  without  dissocia- 
tion (507).  A  simpler  method  of  preparation  is  to  saturate  a  solu- 
tion of  an  acid  alkali  oxalate  with  zirconium  hydroxide.  The  formula 
has  also  been  written  Zr(C2O4R)  .5H2O  where  R  represents  the  am- 
monium radical  or  an  alkali  metal  (576) . 

Tartaric  Acid.  Zirconyl  hydroxide  dissolves  in  tartaric  acid  in  a 
proportion  of  less  than  1  :  1000.  It  is  ten  times  more  soluble  in  an 
ammoniacal  solution  of  ammonium  tartrate.  The  composition  of  the 
precipitate  formed  by  adding  a  solution  of  tartaric  acid  to  solutions 
of  zirconyl  salts  varies  under  differing  conditions  of  precipitation 
(794).  The  results  obtained  by  Hornberger  (356)  do  not  accord  with 
more  recent  investigations.  Rosenheim  and  Frank  (610)  found  that 
on  adding  tartaric  acid  to  a  solution  of  zirconyl  chloride  the  precipi- 
tate settled  well  and  was  easily  filtered.  When  air-dried  it  formed  an 
amorphous  powder,  insoluble  in  water,  easily  soluble  in  mineral  acids 
and  caustic  alkalies.  It  could  be  reprecipitated  from  the  latter  with- 
out alteration  by  the  addition  of  acid.  Various  preparations  under 
differing  conditions  yielded  on  analysis  results  corresponding  to  the 
formula  Zr3(OH)8.C4H406.6H20  (611).  The  analyses  reported  fail 
to  agree  closely.  By  adding  two  atoms  of  hydrogen  the  formula  may 
be  rewritten  2ZrO(OH)2.ZrOC4H406.7H2O.  This  is  probably  only 
one  of  several  basic  tartrates  which  may  be  formed  under  more  widely 
differing  conditions.  The  solubility  in  caustic  alkali  indicates  the 
existence  of  double  tartrates.  Rimbach  and  Schneider  (593)  observed 
that  the  addition  of  solutions  of  zirconyl  salts  to  alkali  tartrate  solu- 
tions increased  the  action  on  polarized  light.  The  above-mentioned 
basic  tartrate,  when  dissolved  in  just  the  necessary  amount  of  caustic 
alkali  and  the  solution  evaporated  to  a  syrupy  consistency,  gave  small, 
needlelike  crystals  which  were  very  soluble  in  water.  Analysis  gave 
the  composition  as  K2C4H406.ZrOC4H40G.3H20,  which  was  reported 
(609)  as  ZrO(C4H406K)2.3H2O.  The  same  compound  was  prepared 
by  mixing  solutions  so  as  to  give  the  ratio  two  molecules  of  tartaric 
acid,  one  molecule  of  zirconyl  nitrate,  and  four  molecules  of  potassium 
hydroxide.  Potassium  nitrate  first  crystallized  out  and  then  potas- 
sium zirconium  tartrate.  The  analogous  sodium  salt  was  not  ob- 
tained. Solutions  of  zirconium  tartrate  in  ammonium  hydroxide  gave 
products  which  were  unstable,  losing  ammonia  on  standing.  Rosenr 


114  ZIRCONIUM  AND  ITS  COMPOUNDS 

heim  and  Frank  (610)  looked  upon  the  fact  that  many  of  these  com- 
pounds with  organic  acids,  when  prepared  under  varying  conditions, 
show  a  constant  composition  as  evidence  that  they  are  definite  com- 
pounds and  not  adsorption  compounds  as  maintained  by  Miiller  (512). 

Benzole  Acid.  A  compound  of  the  normal  zirconium  benzoate 
with  ZrCl2  has  been  prepared  (611)  by  the  action  of  an  ethereal  solu- 
tion of  benzoic  acid  at  the  boiling  temperature  upon  zirconium  tar- 
trate,  the  boiling  being  continued  so  long  as  hydrogen  chloride  was 
liberated.  The  reaction  proceeds  according  to  the  equation 
ZrCl,  +  2C6H5 .  C02H  =  ZrCl2  (C6H5 .  C02)  2  +  2HCL  The  radical 
ZrCl2  functions  apparently  as  the  radical  ZrO.  Stronger  monocar- 
boxylic  acids  of  the  aliphatic  series  liberate  all  four  of  the  chlorine 
atoms  (see  Formic  and  Acetic  Acids). 

By  this  same  method  a  similar  compound  was  obtained  with  ethyl 
benzoate.  Two  molecules  of  this  ester  and  one  of  zirconium 
tetrachloride  were  heated  with  a  reflux  condenser.  There  was  no 
evolution  of  hydrogen  chloride.  Crusts  of  brilliant  crystals  formed. 
The  composition  was  found  to  be  ZrCl4(C6H5.C02.C2H5)2.  These 
crystals  were  unstable  in  the  air,  liberating  hydrochloric  acid.  Similar 
compounds  were  given  with  other  esters,  ketones,  and  aldehydes  (611). 

Basic  zirconyl  benzoates  have  been  prepared  by  Venable  and  Blay- 
lock  (746)  by  adding  a  saturated  aqueous  solution  of  benzoic  acid 
to  a  solution  of  zirconyl  chloride.  If  the  solution  were  cold  the  pre- 
cipitate was  finely  granular,  forming  only  after  prolonged  standing 
and  settling  slowly.  It  was  evident  that  the  precipitation  was  only 
partial.  When  the  solutions  were  heated  to  boiling  the  precipitate 
was  gelatinous,  settling  readily  and  easily  washed  and  filtered.  Both 
varieties  of  precipitate  were  dissolved  by  ammonium  hydroxide.  The 
precipitate  was  washed  free  of  chlorine  by  hot  water.  The  white 
precipitate  continued  to  lose  water  on  heating  at  100°  and  darkened, 
hence  the  analyses  were  made  on  air-dried  samples.  The  different 
preparations  formed  under  varied  conditions  of  dilution  and  washing 
were  analyzed.  The  composition  of  these  was,  respectively: 

No.  1,  ZrO(OH)2.2ZrO(C6H5.C02)2.6H20; 
No.  2,  ZrO(OH)2.3ZrO(C6H5.C02)2.16H20; 
No.  3,  ZrO(OH)2.6ZrO(C6H5.C02)2.6H20. 

Apparently  no  definite  compound  was  formed  but  a  series  of  basic 
zirconyl  benzoates  representing  various  degrees  of  hydrolysis.  These 
may  be  mixtures  or  adsorption  compounds  of  zirconyl  benzoate  and 


ORGANIC  COMPOUNDS  115 

the  colloidal  hydroxide.  It  is  noticeable  that  the  formula  assigned 
to  No.  1  corresponds  to  that  reported  by  Rosenheim  and  Frank  (610) 
to  the  tartrate  prepared  by  them  in  a  somewhat  similar  manner.  This 
may  be  due  to  a  coincidence  of  conditions  under  which  the  experi- 
ments were  made,  or  may  furnish  an  argument  for  the  existence  of 
this  as  a  definite  compound  formed  at  a  certain  stage  in  the  progress 
of  the  hydrolysis. 

Salicylic  Acid.  The  compound  corresponding  to  the  one  with 
benzoic  acid  was  prepared  (611)  by  the  same  method.  Zirconium 
tetrachloride  was  added  to  an  anhydrous  ethereal  solution  of  salicylic 
acid  and  the  whole  kept  at  boiling  temperature  so  long  as 
hydrogen  chloride  escaped.  Analysis  gave  the  composition  as 
ZrCl2  (OC6H4 .  C02 .  CH3)  2.  The  hydrogen  of  the  hydroxyl  group  com- 
bines with  the  chlorine  to  form  the  hydrogen  chloride.  It  is  obtained 
in  the  form  of  a  white,  crystalline  crust.  When  the  same  reaction  was 
tried  with  salicylaldehyde  (the  ZrCl4  being  suspended  in  chloro- 
form) a  deep  yellow,  crystalline  powder  with  the  composition 
ZrCl2(O.C6H4.CHO)2  was  obtained.  Similar  results  were  obtained 
with  other  monohydroxy  acids  and  aldehydes  and  also  with  ketones, 
but  individual  mention  of  these  was  not  made  (611).  As  already 
stated  under  the  appropriate  heading,  this  reaction  gives  with  ali- 
phatic acids  compounds  in  which  all  of  the  chlorine  is  replaced  by  the 
organic  radical. 

A  basic  zirconyl  salicylate  was  prepared  by  Venable  and  Giles 
(748).  A  saturated  solution  of  salicylic  acid  was  added  to  a  solu- 
tion of  zirconyl  chloride.  A  precipitate  formed  on  standing  or  boil- 
ing. Three  preparations  were  made  in  which  the  conditions  varied 
more  or  less,  especially  as  to  dilution  and  amount  of  water  used  in 
washing.  '  In  other  words,  there  was  no  effort  at  reproducing  the 
exact  conditions  as  to  factors  in  hydrolysis.  The  analyses  gave  re- 
sults showing  the  same  product  formed  in  the  three  experiments.  The 
composition  was  2ZrH(OH2.3ZrO(C7H603)2.  This  compound  was 
less  stable  than  the  basic  benzoic,  decomposition,  beginning  at  100°, 
and  the  white  precipitates  were  quite  black  at  160°.  The  samples 
were  merely  air-dried  and  contained  varying  percentages  of  water. 
This  tendency  to  form  one  stable  basic  salicylate  shows  a  decided 
difference  from  the  benzoates. 

The  formation  of  a  pyro-racemate  (propanonate)  has  been  re- 
ported (65);  an  acetyl-acetonate  (69);  and  a  valerianate  (712). 

Hydrocyanic  Acid  and  Thiocyanic  Acid.    A  solution  of  potassium 


116  ZIRCONIUM  AND  ITS  COMPOUNDS          ( 

cyanide  gives  a  precipitate  with  solutions  of  zirconyl  salts  according 
to  Weibull  (794) .  This  has  not  been  further  investigated. 

When  barium  cyanide  is  added  in  equivalent  amount  to  a  solution 
of  zirconyl  sulphate,  barium  sulphate  is  precipitated  and  zirconyl- 
cyanide  remains  dissolved.  The  solution  is  colorless  and  easily  de- 
composed (794). 

The  thiocyanate  has  been  prepared  by  Hornberger  (356)  by  add- 
ing barium  thiocyanate  to  a  solution  of  zirconium  sulphate.  After 
removing  the  precipitated  barium  sulphate  a  colorless  powder  was 
obtained.  This  was  unstable  in  the  air,  becoming  yellow.  Placed 
over  sulphuric  acid  a  yellow,  amorphous  mass,  which  turned  brown 
on  the  water  bath,  was  left.  The  analysis  gave  the  composition  as 
approximately  Zr(CNS)2.  The  value  of  this  work  is  doubtful  as  the 
author  assumes  zirconium  to  be  bivalent.  Rosenheim  and  Frank 
(610)  saturated  HSCN  in  alcoholic  solution  with  Zr(OH)4  and  then 
precipitated  with  ether.  The  precipitate  was  white  and  easily  solu- 
ble in  water  or  alcohol.  Double  salts  of  the  type  M2H2Zr(SCN)6 
were  obtained  with  pyridine  and  quinoline.  These  were  crystalline, 
deliquescent,  and  unstable  in  air. 

F err o cyanides.  The  ferrocyanide  was  investigated  by  Weibull 
(794),  Hornberger  (356),  and  de  Boisbaudran  (88).  The  method  of 
precipitation  was  from  hot  solutions  of  zirconium  salts.  Hornberger 
reported  a  compound,  Zr3Fe2(CN)12  or  3Zr(CN)2.2Fe(CN)3.  The 
assumption  of  bivalence  for  zirconium  would  seem  to  make  this  work 
unreliable.  De  Boisbaudran  (88)  stated  that  ferrocyanide  gave  a 
yellow  precipitate  in  solutions  of  zirconium  salts  even  when  very  acid 
and  dilute.  Rose  (600)  reported  a  precipitate  formed  with  potassium 
ferricyanide. 

Compounds  of  the  Tetrahalides  with  Organic  Radicals,  etc. 

The  tetrahalides  of  zirconium  form  a  number  of  addition  com- 
pounds with  the  amines  analogous  to  those  formed  with  ammonia,  also 
with  organic  bases.  Substitution  compounds  are  formed  also  with 
various  organic  radicals  in  which  part  or  all  of  the  halogen  is  sub- 
stituted. The  compounds  formed  with  the  tetrachloride  have  been 
the  chief  ones  investigated. 

In  all  such  reactions  in  which  these  tetrahalides  are  concerned 
water  must  be  absent.  Since  the  tetrachloride  reacts  with  alcohol, 
giving  off  ethyl  chloride  when  heated  and  leaving  zirconium  hydroxide 


ORGANIC  COMPOUNDS  117 

(356,  337) ,  this  also  can  not  be  used  as  a  medium.  Attempts  to  form 
alcoholates,  however,  have  failed  (609).  The  tetrachloride  is  soluble 
in  ethyl  ether  with  indications  of  some  reaction,  since  in  concentrated 
solutions  there  are  formed  yellow  crystals  which  are  dissolved  on 
further  addition  of  ether  and  are  rapidly  decomposed  independently 
of  the  presence  of  air.  Similar  crystals  are  formed  by  the  tetraiodide 
and  the  analysis  indicates  the  presence  of  ZrI4.4(C2H5)2O.  As  alco- 
hol was  used  in  the  reaction  and  the  analyses  were  imperfect,  the 
existence  of  this  compound  is  in  doubt.  The  crystals  dissolved  in 
water  with  violent  reaction  (674).  Sometimes  the  reaction  has  been 
brought  about  by  suspending  the  tetrachloride  in  a  medium  such  as 
chloroform.  Carbon  tetrachloride  might  also  be  used,  being  inactive 
toward  zirconium  tetrachloride.  Interaction  between  the  vapor- 
ized substances  has  been  seldom  tried.  The  vapor  of  zirconium  tetra- 
chloride was  found  not  to  react  with  certain  organo-metallic  com- 
pounds, such  as  mercury  ethyl  or  phenyl.  It  does  react  at  tempera- 
tures over  300°,  with  methane  or  acetylene.  These  reactions  have  not 
been  fully  studied. 

Addition  Compounds.  As  double  compounds  with  ammonia  are 
formed  by  passing  dried  ammonia  through  an  ethereal  solution  of 
zirconium  tetrachloride,  so  similar  compounds  can  be  prepared  with 
the  amines  and  organic  bases.  Matthews  (471)  prepared  a  methyla- 
mine  compound,  ZrCl4 .  4CH3 .  NH2 ;  ethylamine,  ZrCl4 .  4C2H5 .  NH2 ; 
propylamine,  ZrCl4.4C3H7.NH2;  pyridine,  ZrCl4 .  2C5H5N.  Pyridine 
hydrochloride,  ZrCl4.2C5H6.N.HCl,  was  prepared  by  Rosenheim  and 
Frank  (609)  by  saturating  alcohol  in  the  cold  with  hydrogen  chloride, 
then  saturating  this  with  zirconium  hydroxide,  again  saturating  with 
hydrogen  chloride,  and  adding  to  this  a  concentrated  solution  of 
pyridine  hydrochloride.  The  micro-crystals  obtained  were  fairly 
stable  in  the  air  after  washing  with  alcohol  and  ether. 

When  anilin  is  added  to  a  solution  of  zirconium  tetrachloride  in 
ether  a  gray  precipitate,  which  seems  to  be  stable  when  dry,  is  formed. 
This  has  the  composition  ZrCl4 .  4C6H5NH2  (471).  In  the  same  way 
was  formed  a  compound  with  toluidine  with  similar  composition, 
ZrCl4.4C7H7.NH2.  A  gray-brown  precipitate  having  the  formula 
ZrCl4.2C10H7NH2  was  given  with  p-naphthylamine  and  an  analogous 
compound,  ZrCl4.2C9H7N,  was  formed  with  chinolin  (471).  A  chino- 
lin  hydrochloride  has  been  prepared  (609).  This  was  microcrystal- 
line  and  less  stable  than  the  corresponding  pyridine  hydrochloride. 
Its  composition  was  ZrCl4.2C9H7.N.HCl. 


118  ZIRCONIUM  AND  ITS  COMPOUNDS 

Chauvenet  (125)  prepared  addition  compounds  with  pyridine  by 
dissolving  zirconium  tetrachloride  in  pyridine  and  evaporating  the 
solution,  water  being  excluded.  Crystals  showing  the  existence  of 
two  compounds  were  obtained.  First,  there  was  a  compound, 
ZrCl4.4C5H5N,  which  decomposed  at  room  temperature,  more  rapidly 
at  50°,  or  in  vacuum  at  15°.  The  loss  by  weight  ceased  when  the 
composition  ZrCl4.2C5H5N  was  reached.  The  latter  decomposed  at 
70°-80°. 

Zirconium  tetrabromide  forms  analogous  compounds:  With  ethyla- 
mine,  ZrBr4 . 4C2H5NH2 ;  with  pyridin,  ZrBr4.2C5H5N;  with  anilin, 
ZrBr4.4C6H5NH2  (471).  There  is  also  a  pyridin  bromhydrate, 
ZrBr4.2C5H5N.HBr,  which  is  much  less  stable  than  the  tetrachloride 
compound  (609). 

Zirconium  tetraiodide  heated  in  vapor  of  ethylamine  gives  with 
strong  evolution  of  heat  a  compound,  ZrI4.6C2H5.NH2.  Other  ex- 
periments in  preparing  addition  compounds  with  the  tetraiodide  have 
been  reported  (674) ,  but  the  methods  adopted  were  open  to  criticism 
and  analytical  results  unsatisfactory. 

Zirconium  thiocyanate  also  forms  compounds  with  pyridin  and 
chinolin  analogous  to  those  formed  with  the  tetrahalides.  The  method 
of  preparation  is  similar  (610) .  A  concentrated  solution  of  thiocyanic 
acid  in  absolute  alcohol  was  saturated  with  zirconium  hydroxide  and 
pyridin  thiocyanate  added.  A  yellowish,  crystalline  precipitate  was 
formed.  It  was  extremely  unstable.  The  analyses  indicated  the  com- 
position as  Zr(SCN)6.HSCN.2C5H6N.  Similarly  there  was  obtained 
with  chinolin  a  compound  with  like  properties  to  which  the  formula 
Zr(SCN)6.HSCN.2C9H8N2  was  assigned. 

Hinsberg  (337)  found  that  when  ZrCl4  was  dissolved  in  absolute 
alcohol  and  the  solution  boiled  ethyl  chloride  was  given  off  and  zir- 
conium hydroxide  left.  When  zinc  ethyl  was  added  to  powdered  zir- 
conium tetrachloride  and  heated  to  180°  in  an  atmosphere  of  carbon 
dioxide  butane  was  given,  due  doubtless  to  the  presence  of  some 
water.  Rosenheim  and  Herzmann  (611)  concluded  from  their  experi- 
ments that  ZrCl4  formed  a  molecular  compound  with  methyl  ether. 
This  they  were  unable  to  get  in  a  pure  state  and  subject  to  analysis. 
Molecular  compounds  were  formed  with  esters  by  heating  with 
ethereal  solutions  of  ZrCl4.  For  instance,  when  a  water-free  ethereal 
solution  of  two  molecules  of  benzoic  esters  was  mixed  with  an  ethereal 
solution  of  one  molecule  of  ZrCl4  and  boiled  with  a  reflux  condenser 
a  crust  of  white  crystals  formed.  These  were  unstable  in  the  air. 


ORGANIC  COMPOUNDS  119 

The  analysis  gave  ZrCl4  (C6H5 .  C02 .  C2H5)  2.  Ketones,  aldehydes,  and 
esters  of  various  monobasic  acids  gave  the  same  reaction.  In  this 
reaction  no  evolution  of  hydrogen  chloride  was  observed. 

Peters  (540)  found  that  ZrCl4  did  not  react  at  200°  with  C2H5I 
nor  with  Hg(C2H5)2.  If,  however,  slight  moisture  were  present  the 
reaction  ZrCl4  +  2Hg(C6H5)2  +  H20  =  ZrOCl2.2HgCl.C6H5  +2C6H6 
took  place.  This  substance  was  soluble  in  ether.  When  heated  in  a 
vacuum  mercury  phenyl  chloride  sublimed.  Mercury  ethyl  and  mer- 
cury o-tolyl  gave  no  reaction. 

Jefferson  (373)  has  recorded  precipitates  as  being  formed  by  the 
action  of  a  large  number  of  organic  substances  upon  an  aqueous  solu- 
tion of  zirconium  nitrate.  Among  these  were  anilin,  orthotoluidin, 
xylidin,  dimethylanilin,  di-ethylanilin,  benzylamin,  pyridin,  piperidin, 
chinolin,  etc.  The  nature  of  these  precipitates  is  unknown.  Hart- 
well  (291)  also  reports  a  number  of  such  precipitates. 

Kolb  (405)  added  antipyrin  to  an  acid  solution  of  zirconyl  nitrate, 
evaporated  on  a  water  bath  to  a  syrupy  liquid,  and  then  allowed  this 
to  solidify  over  a  dehydrating  agent.  The  formula  assigned  on  anal- 
ysis of  the  product  was  Zr(N03)4.6C11H12N20. 


Chapter  X 

Analytical  Methods 

Qualitative 

No  flame  test  is  given  by  zirconium.  It  can  of  course  be  identified 
by  the  characteristic  lines  given  in  the  spectrum,  but  this  makes  too 
great  a  demand  upon  the  equipment  and  skill  of  the  ordinary  analyst. 
So  delicate  a  test  would  doubtless  reveal  its  presence  as  very  widely 
distributed.  Pereira-Forjaz  (539)  has  made  a  spectrographic  study 
of  Portuguese  minerals,  finding  zirconium  in  a  number  of  them. 
Microchemical  detection  has  been  recommended  by  Behrens  (37), 
who  used  the  strongly  refracting  crystals  of  rubidium  fluozirconate- 
rubidium  fluoride,  RbF.Rb2ZrF6.  Sodium-zirconium  oxalate  crys- 
tals and  also  those  of  the  corresponding  potassium  compound  have 
been  used  for  this  purpose  (232,  304) .  Since  one  or  both  the  double 
fluorides  and  double  oxalates  may  be  formed  and  the  properties  of 
the  crystals  differ,  these  microchemical  tests  would  seem  to  be  unreli- 
able unless  definite  conditions  of  formation  are  maintained.  The  crys- 
talline form  of  zirconyl  chloride  has  also  been  proposed  as  a  test. 
This  form  varies  with  conditions  of  crystallization,  and  extent  of 
hydrolysis. 

Blowpipe  reactions  for  zirconia  have  been  given  by  Florence  (225). 
The  behavior  of  zirconia  in  borax  beads  and  in  those  of  microcosmic 
salt  has  been  described  by  Wunder  (825) .  A  number  of  investigators 
(291,  373,  466)  have  reported  the  precipitates  given  by  organic  bases. 
Brush  (111)  found  that  zirconium  salts  gave  an  orange-red  with  tur- 
meric paper.  According  to  Noyes  (528) ,  the  color  is  more  accurately 
described  as  pink.  Titanium  gives  the  same  color.  Kaserer  (383) 
recommended  as  a  color  reaction  that  given  by  pyrogallol-aldehyde. 
This  reagent  gives  with  solutions  of  zirconium  salts  a  yellow  colora- 
tion and  on  boiling  a  dirty  yellow  precipitate  and  colorless  solution. 
The  same  reaction  is  given  with  thorium  salts. 

A  much  used  qualitative  separation  and  detection  is  obtained  by 
precipitation  of  the  mixed  chlorides  with  sodium  hydroxide  in  mod- 

120 


ANALYTICAL  METHODS  121 

erate  excess.  The  hydroxides  of  Zr,  Fe,  Mn,  Co,  Ni,  Ti,  and  U  remain 
undissolved.  These  are  washed  and  then  dissolved  in  hydrochloric 
acid,  the  percentage  of  acid  being  brought  up  to  20-32.  On  shaking 
with  ether  zirconium  chloride  is  left  in  the  aqueous  layer,  though 
several  shakings  with  fresh  ether  may  be  necessary  (528). 

Biltz  and  Mecklenburg  (72)  recommended  a  most  delicate  and 
useful  qualitative  test.  The  solution  supposed  to  contain  zirconium 
is  strongly  acidified  with  nitric  or  hydrochloric  acid.  A  few  drops  of 
sodium  phosphate  are  added  and  the  solution  warmed.  A  white, 
gelatinous  precipitate  is  given  when  as  little  as  0.0005  per  cent,  of 
zirconia  is  present.  No  other  element  known  to  the  authors  gave 
such  a  precipitate  in  strongly  acid  solution.  Iron,  aluminum,  the  rare 
earths,  beryllium,  titanium,  thorium,  and  silicon  gave  no  reaction. 
When  a  mineral  is  to  be  examined  it  can  be  fused  in  a  soda  bead  in  the 
oxidizing  flame,  the  bead  dissolved  in  excess  of  hydrochloric  acid, 
boiled,  filtered,  and  a  drop  of  the  phosphate  solution  added.  The  test 
is  not  applicable  if  phosphoric  acid  is  present  in  the  mineral. 

In  analytical  work  with  zirconium  it  should  be  borne  in  mind 
that  all  aqueous  solutions  of  its  salts  have  an  acid  reaction  on  account 
of  the  liberation  of  free  acid  by  hydrolysis.  Hence  neutralization  is 
temporary  and  even  after  carrying  out  the  hydrolysis  by  boiling  is 
only  approximate. 

Quantitative  Determination 

Zirconium  in  combination  with  a  volatile  or  organic  acid  is  usually 
determined  by  direct  ignition  and  weighing  as  Zr02.  Errors  may  arise 
from  two  causes.  In  the  first  place,  certain  acid  radicals  are  per- 
sistently retained,  even  after  hours  of  heating  over  a  blast  lamp. 
In  the  case  of  chlorides,  for  instance,  a  fraction  of  a  per  cent  of  the 
chlorine  is  thus  held.  This  small  amount  retained  does  not  seriously 
impair  the  results  in  ordinary  analyses,  but  becomes  noteworthy  where 
strict  accuracy  is  required.  The  error  here  is  in  the  direction  of 
results  that  are  too  high.  A  second  possible  error  arises  from  the 
extremely  fine  subdivision  of  the  zirconia  and  the  ease  with  which  it 
is  entrained  and  carried  off  by  gas  currents,  such  as  those  resulting 
from  the  burning  of  organic  acids  or  the  gases  from  the  burner.  This 
loss  is  not  prevented  by  the  presence  of  ammonium  compounds  as 
maintained  by  Bailey,  but  rather  accentuated.  If  nitric  acid  is  the 
one  present  the  volatile  radical  can  be  driven  off  without  loss  under 


122  ZIRCONIUM  AND  ITS  COMPOUNDS 

the  proper  conditions.  The  error  here  is  in  the  direction  of  results 
that  are  too  low.  Hence  this  may  r  in  part  counterbalance  the  error 
mentioned  above. 

If  the  zirconium  hydroxide  has  been  precipitated  by  means  of 
ammonium  hydroxide  and  so  is  in  the  form  of  hydroxide,  there  is 
another  source  of  loss  which  must  be  reckoned  with.  Whenever  an 
aqueous  solution  of  a  zirconium  salt  stands  or  is  heated  hydrolysis 
takes  place,  so  the  hydroxide  is  always  present  and  the  necessary 
precautions  for  this  condition  must  virtually  always  be  applied.  It 
has  been  found  that  unless  the  water  has  been  driven  off  at  least  to 
1  p.c.  or  less  at  a  temperature  below  300°  then,  on  raising  to  that 
temperature  or  higher,  the  remaining  molecules  of  water  are  lost 
with  the  evolution  of  much  energy  accompanied  by  incandescence  and 
tiny  explosions,  thus  causing  the  practical  loss  of  substance.  For 
careful  work  it  has  been  found  best  to  heat  in  an  electric  oven  or  air 
bath  at  a  temperature  between  250°  and  275°  for  an  hour  or  so.  The 
water  in  the  hydroxide  is  thus  reduced  below  the  danger  limit.  For 
organic  radicals  the  temperature  should  be  raised  stepwise  to  250°  so 
as  to  insure  the  burning  taking  place  at  as  low  a  temperature  as  prac- 
ticable and  a  reasonably  slow  evolution  of  the  gases.  After  the  in- 
complete drying  or  burning  the  temperature  is  raised  to  300°-500° 
and  the  last  traces  of  water  driven  off  at  900°-1000°.  Analyses  car- 
ried out  in  this  way  will  give  results  higher  usually  by  some  tenths 
of  a  per  cent  than  those  obtained  by  direct  and  rapid  ignition. 

In  many  cases,  as  separations,  etc.,  it  is  desirable  that  the  zir- 
conium be  precipitated  as  hydroxide.  Since  this  colloidal  hydroxide 
retains  persistently  potassium  or  sodium  hydroxide,  this  precipitation 
should  always  be  done  with  ammonium  hydroxide.  The  precipitation 
is  practically  complete  and  the  solvent  power  of  the  precipitant  when 
used  in  slight  excess  is  negligible.  The  other  hydroxides  exert  a  slight 
solvent  action.  For  the  reason  already  given  the  ammonium  salts 
formed  should  be  thoroughly  washed  out  before  ignition.  This  is 
more  or  less  difficult  according  to  the  condition  of  the  gelatinous  pre- 
cipitate. 

Various  inorganic  and  organic  substances  have  been  recommended 
as  precipitating  the  zirconium  more  or  less  completely  from  aqueous 
solutions,  but  on  account  of  the  hydrolysis  going  on  in  the  solution, 
and  hence  the  varying  basicity  of  the  salts  contained  in  it,  there  is 
little  certainty  as  to  the  nature  of  the  product  obtained  on  ignition 
unless  the  acid  radical  can  be  entirely  volatilized,  leaving  only  pure 


ANALYTICAL  METHODS  123 

zirconia.  Thus  oxalic  acid  has  been  used  (741,  617,  621) ;  lactic  acid 
or  salicylic  acid  (38,  746) ;  thiosulphate  (686,  325) ;  sodium  azide 
(157) ;  acetic  acid  (276) ;  chromate  (276,  748) ;  alkaline  iodate  (169, 
102,  751);  sulphurous  acid  (31). 

The  precipitation  with  phosphoric  acid  or  an  alkali  phosphate  has 
been  frequently  made  use  of  in  certain  separations,  determining  the 
zirconium  as  phosphate,  but  the  composition  of  this  precipitate  varies 
according  to  the  extent  of  the  hydrolysis.  It  has  been  chiefly  used 
where  the  amount  of  zirconium  present  is  quite  small  and  the  varia- 
tions in  composition  negligible.  The  precipitate  approximates  in  com- 
position ZrP20T  (677) .  The  use  of  the  empirical  factor  Zr  =  0.3828 
has  also  been  suggested  (216,  516) .  Precipitation  by  means  of  sodium 
subphosphate  has  also  been  suggested  (412) . 

Separation  from  Other  Elements 

Precipitation  by  means  of  ammonium  hydroxide  furnishes  a 
method  for  the  separation  of  zirconium  from  a  number  of  other  ele- 
ments not  precipitated  by  this  reagent  in  dilute  solutions.  The  col- 
loidal nature  of  zirconium  hydroxide  and  its  strong  adsorptive  power 
must,  however,  be  kept  in  mind.  In  some  cases  the  thorough  wash- 
ing out  of  alkalies  and  other  substances  is  difficult  even  with  pro- 
longed washing.  Aluminum,  manganese,  the  iron  group,  titanium, 
and  uranium  are  precipitated  along  with  the  zirconium. 

The  separation  from  aluminum  by  means  of  an  alkali  iodate  has 
been  investigated  (169,  102).  The  precipitation  is  quantitative  in 
the  presence  of  an  excess  of  the  reagent  and  also  of  nitric  acid.  lodic 
acid  may  be  used  instead  of  the  iodate  (751).  While  this  method 
will  separate  zirconium  from  a  number  of  other  elements,  it  can  not 
be  relied  on  for  separation  from  thorium  and  titanium  (412) . 

A  complete  and  satisfactory  separation  from  iron  has  been  the 
object  of  much  investigation,  since  this  element  is  the  most  usual 
concomitant  of  zirconium  and  must  be  removed  for  a  number  of  in- 
dustrial uses.  A  complete  list  of  methods  used  or  recommended  would 
have  little  practical  bearing,  as  many  of  them  are  out  of  date  and 
abandoned.  For  the  remainder  only  the  general  principles  involved 
can  be  indicated. 

The  weighed  mixture  of  oxides  may  be  heated  in  a  current  of 
hydrogen  (595,  272,  273,  164,  165)  or  of  phosgene  (762)  or  the  iron 
may  be  titrated  (684) .  The  mixed  oxides  may  be  treated  with  hydro- 


124  ZIRCONIUM  AND  ITS  COMPOUNDS 

gen  chloride  (312).  The  neutral  solution  may  be  treated  with  sul- 
phur dioxide  or  alkali  sulphites  added  (47,  319,  31),  by- adding  am- 
monium sulphide  in  the  presence  of  tartaric  acid  (573,  118,  356,  238, 
401),  by  treatment  with  hydrogen  peroxide  or  sodium  dioxide  (18, 
238,  188,  191),  by  precipitation  with  nitroso-naphthol  (401),  by  pre- 
cipitation with  thiosulphate  (686,  326,  467).  Electrolytic  dissocia- 
tion has  also  been  investigated  (144,  338).  The  separation  of  zir- 
conium from  iron  in  the  presence  of  titanium  and  also  when  both 
titanium  and  thorium  are  present  has  been  investigated  (188,  189, 
190).  For  separation  from  titanium  a  number  of  methods  have  been 
proposed  (552,  326,  684,  172,  21,  16,  173,  188,  189,  190,  191,  108). 
Some  of  these  make  use  of  hydrogen  peroxide  as  the  precipitant.  This 
precipitates  both  and  the  titanium  may  then  be  determined  colori- 
metrically  (188,  191,  6).  Ammonium  salicylate,  sodium  acetate,  and 
acetone  have  also  been  used.  Fractional  precipitation  by  means  of 
ammonium  hydroxide  at  boiling  temperature  has  been  used  for  sepa- 
ration of  titanium  and  columbium.  The  use  of  oxalic  acid  or  alkaline 
oxalates  has  been  investigated  (246),  but  has  been  found  unreliable 
if  sulphuric  acid  is  present  (617). 

Various  methods  have  been  suggested  for  separation  from  thorium 
(326,  246,  173,  563,  368,  190). 

In  its  natural  occurrence  zirconium  is  always  associated  with 
silicon.  The  separation  here  is  by  the  usual  method  of  heating  with 
hydrofluoric  acid.  There  is  a  necessary  precaution,  however,  namely, 
that  an  excess  of  sulphuric  acid  must  always  be  present;  otherwise 
some  zirconia  will  be  lost  (784).  Some  of  the  sulphuric  acid  radical 
is  also  persistently  retained  and  the  ignition  must  be  carefully  and 
thoroughly  carried  out. 

Cupferron,  which  is  the  convenient  name  for  the  organic  com- 
pound nitroso-phenyl-hydroxylamme-ammonium,  has  been  proposed 
as  a  precipitant  for  the  separation  and  determination  of  zirconium. 
It  was  found  that  zirconium  could  be  quantitatively  precipitated  by 
it  in  acid  solutions  (615).  At  first  the  amount  of  acid  (sulphuric) 
which  might  be  present  could  amount  to  as  much  as  5-7%  p.c.  by 
volume  (705),  and  this  was  later  confirmed  (218).  The  method  was 
used  successfully  by  Brown  (106),  and  Lundell  and  Knowles  (458) 
have  recently  shown  that  40  p.c.  of  sulphuric  acid  may  be  present. 
Tartaric  acid  also  does  not  interfere.  Nitric  acid  decomposes  the 
reagent.  The  iron  must  first  be  removed  by  precipitation  with  am- 
monium sulphide  in  the  presence  of  tartaric  acid.  For  separation 


ANALYTICAL  METHODS  125 

from  aluminum  the  solution  must  be  highly  acid  and  the  presence  of 
tartaric  acid  is  desirable.  The  presence  of  platinum  or  boric  acid 
does  not  interfere,  but  that  of  phosphoric  acid  introduces  a  disturbing 
effect.  The  method  is  recommended  as  most  exact.  On  ignition  of 
the  precipitate  zirconia  is  obtained  but  the  usual  precautions  to  pre- 
vent loss  must  be  observed.  See  also  (40). 

The  method  involving  the  use  of  phenylhydrazine  has  been  recom- 
mended (4).  This  and  the  cupferron  method  of  analysis,  as  well  as 
the  phosphate  and  the  thiosulphate,  have  been  comparatively  investi- 
gated (467,  333). 

An  investigation  of  the  various  methods  for  determining  zirconium 
has  been  made  by  Lundell  and  Knowles  (458,  460).  Objections  to 
previous  methods  are  detailed.  The  methods  especially  tested  are 
those  of  Kelly  and  Meyers  (387),  Ferguson  (216,  217),  Johnson  (375, 
376),  Travers  (710),  and  Hillebrand  (333,  334).  A  mode  of  pro- 
cedure is  recommended  for  the  separation  and  determination  of  zir- 
conium, especially  in  steels.  The  final  precipitation  is  by  cupferron, 
giving  zirconia  and  titanic  oxides  on'  ignition.  The  titanium  is  deter- 
mined colorimetrically. 


Chapter  XI 

Technical  Applications  of  Zirconium  and  Its  Compounds 

Precious  Stone 

The  earliest  use  made  of  a  compound  of  zirconium  was  that  of 
the  natural  silicate  as  a  precious  stone.  It  was  known  under  the 
names  zircon,  jargon,  and  hyacinth,  and  in  early  times  was  also  sup- 
posed to  have  medicinal  value.  The  use  of  the  name  hyacinth  among 
the  ancients  was  confusing  as,  besides  the  zircon,  it  sometimes  meant 
the  carbuncle  and  also  a  dark  amethyst.  The  zircon,  known  by 
lapidaries  commonly  as  the  Ceylon  zircon  or  jargon,  was  regarded  as 
distinct  from  the  hyacinth  and  was  usually  colored  fire-red,  yellow, 
yellowish-green,  or  gray.  The  hyacinth  was  distinguished  as  Oriental 
hyacinth.  Its  color  was  deep  red  with  a  touch  of  brown  or  some- 
times of  orange-red.  Zircons  show  a  great  variety  of  colors  from 
colorless  to  red,  brown,  yellow,  green,  gray,  white,  pink,  and  blue, 
besides  intermediate  tints.  They  may  be  translucent  but  ordinarily 
are  opaque. 

On  account  of  its  hardness  (7.5)  the  zircon  is  cut  with  diamond 
powder  or  emery.  It  is  cut  in  the  rose,  table,  or  brilliant  form.  The 
value  depends  chiefly  upon  the  purity  of  the  color.  On  account  of 
its  lustre  and  hardness  it  has  been  substituted  for  the  diamond.  In- 
deed, at  one  time  it  was  supposed  to  be  an  inferior  variety  of  dia- 
mond. It  has  been  used  in  jewelling  watches  and  as  supports  for 
the  knife  edges  of  fine  balances.  There  is  little  demand  for  it  at 
present  in  jewelry  except  in  the  case  of  fine  crystals  of  pure  color. 
At  one  time  it  was  supposed  to  be  peculiarly  appropriate  and  was 
much  used  in  mourning  jewelry.  The  artificial  preparation  of  zircons 
has  been  attempted  (168,  182,  183). 

Oxy-hydrogen  Light 

The  brilliancy  of  the  light  given  off  by  zirconia  in  the  oxy-hydro- 
gen  flame  was  first  observed  by  Hare  (285)  in  1820  in  his  effort  to 
fuse  it.  After  the  development  of  the  Drummond  limelight  it  was 

126 


TECHNICAL  APPLICATIONS  OF  ZIRCONIUM         127 

suggested  that  zirconia  be  used  as  a  substitute  for  the  lime,  offering 
the  advantages  of  slight  absorbing  power  for  carbon  dioxide  or  water. 
In  1868  du  Motay  (507,  508)  used  it  in  one  of  the  lamps  lighting  the 
Tuileries.  Napoleon  III  was  so  pleased  with  the  result  that  he  ordered 
its  installation  in  all  of  the  lamps  illuminating  the  court  and  gardens. 
The  zirconia  light  attracted  much  attention  on  the  part  of  inventors 
and  others  (66,  117,  167,  199,  287,  404,  451,  482,  535,  545,  657,  700, 
740).  On  account  of  the  purity  of  the  light  and  the  high  emissive 
power  of  the  zirconia  it  was  recommended  for  scientific  use  (433), 
such  as  polariscopes,  spectroscopes,  etc.,  but  this  more  especially 
refers  to  the  next  form. 

Gas  Mantles 

With  the  introduction  of  the  Welsbach  mantles  interest  in  the 
Drummond  light  diminished.  The  first  incandescent  mantles  made 
by  Welsbach  in  1880  consisted  essentially  of  zirconia  (810).  Later 
this  was  largely  substituted  by  the  oxides  of  thorium  and  cerium, 
which  have  a  higher  emissive  power.  Zirconia  is  used  in  admixture 
with  these  and  other  rare  earths  (679). 

Incandescent  Filaments 

A  number  of  attempts  have  been  made  to  use  metallic  zirconium 
in  the  form  of  filaments  in  incandescent  electric  lamps.  Its  electrical 
conductivity  and  high  fusing  point  should  render  it  quite  suitable  for 
this  purpose.  Korolkow  (411)  has  made  an  examination  of  the  elec- 
trical resistance,  emissive  power,  and  expansion  coefficient  of  zir- 
conium filaments  but  such  determinations  are  considerably  affected  by 
the  presence  of  even  small  amounts  of  impurities.  One  difficulty 
which  has  to  be  met  is  the  preparation  of  pure  zirconium  on  a  com- 
mercial scale  and  at  a  reasonable  cost.  Most  of  the  experiments  with 
zirconium  filaments  have  been  carried  out  with  the  more  or  less  impure 
metal,  sometimes  associated  with  the  carbide,  which  itself  has  been 
said  to  be  unsuitable  for  the  purpose.  The  properties  of  zirconium 
seem  to  favor  its  use  as  a  substitute  in  part  for  tungsten  should  the 
difficulties  in  the  way  of  its  commercial  production  in  a  pure  form 
be  overcome,  and  its  abundance  and  wide  distribution  would  speedily 
make  it  replace  the  more  costly  metal.  [See  also  Alloys.]  A  number 
of  patents  bearing  on  the  manufacture  of  the  filaments  have  been  taken 
out  (418-423).  [See  also  Weber  (769)  and  Wedding  (771,  772).] 


128  ZIRCONIUM  AND  ITS  COMPOUNDS 

According  to  Meyer  (486),  investigators  who  have  succeeded  in  pro- 
ducing malleable  zirconium  state  that  it  has  remarkable  properties 
which  fit  it  for  use  in  the  chemical  laboratory  as  a  substitute  for 
platinum.  So  far  nothing  has  been  published  on  this  subject. 

Reduction  of  Metals 

A  patent  has  been  granted  (385)  for  the  use  of  ores  containing 
zirconium  in  extracting  gold,  platinum,  and  other  noble  metals.  The 
supposition  is  that  zirconium  in  the  metallic  state  is  the  active  agent. 
Neither  the  chemistry  nor  the  object  of  this  patent  is  easy  to  unravel. 

There  is  another  patent  (213)  for  the  use  of  zirconium,  its  alloys 
with  magnesium  or  aluminum,  its  carbide  or  phosphide,  as  a  means 
of  reducing  other  metals  or  forming  alloys  with  them.  The  reaction 
is  said  to  be  exothermic  and  hence  proceeds  from  its  own  heat  after 
starting. 

Alloys 

Various  alloys  of  zirconium  have,  been  formed.  The  ferro  and 
nickel  alloys  promise  the  greater  usefulness.  Bronzes  have  also  been 
made.  Cobalt,  aluminum,  and  magnesium  alloys  have  been  placed  on 
the  market.  Ferro-zirconium  has  been  recommended  in  steel  manu- 
facture for  removing  oxygen  and  nitrogen.  It  has  been  offered  com- 
mercially, containing  40-90  p.c.  of  zirconium.  Small  percentages  of 
titanium  have  also  been  introduced. 

The  technically  important  alloys,  chiefly  those  with  metals  of  the 
iron  group,  are  mentioned  under  Patents.  In  the  earlier  attempts 
to  prepare  the  pure  metal,  certain  alloys  or  zirconides,  which  led  to 
confusion  in  the  descriptions  of  the  metal,  were  obtained.  With 
aluminum  there  were  made  preparations,  some  crystalline,  which  con- 
tained varying  proportions  of  aluminum  (713,  714,  230,  489,  776). 
Such  formulas  as  Zr3Al4  and  ZrAl2  have  been  assigned  to  these.  Sim- 
ilar alloys  were  formed  when  magnesium  was  used  instead  of  alumi- 
num. There  seems  to  be  no  tendency  to  alloy  with  metals  of  the 
alkali  nor  alkaline  earth  groups,  nor  with  lead  or  copper.  The  alloys 
are  often  formed  by  thermo-electric  or  alumino-thermic  processes. 

It  is  claimed  that  these  alloys  are  not  subject  to  oxidation  and 
that  they  are  very  resistant  to  chemical  reagents.  The  alloys  have 
a  metallic  lustre  and  some  of  them  take  a  silvery,  steel-like  polish. 
They  are  readily  malleable  and  may  find  a  use  as  filaments  for 


TECHNICAL  APPLICATIONS  OF  ZIRCONIUM         129 

incandescent  lamps.  Such  filaments  are  claimed  to  have  the  power  of 
selective  radiations;  in  other  words,  emit  more  light  than  corresponds 
to  the  temperature  to  which  they  are  heated  by  the  electric  current. 
This  implies  a  considerably  lower  wattage  per  candle  power  than  is 
now  required  by  the  average  metal  filament  lamp  (486).  Analysis 
of  one  such  alloy  shows  zirconium,  65  p.c.;  iron,  26  p.c.;  titanium, 
0.12  p.c.;  and  al,  7.7  p.c.  These  alloys  are  produced  by  reduction 
with  finely  divided  aluminum,  together  with  the  mixed  oxides  of  iron, 
titanium,  or  whatever  metal  it  is  desired  to  introduce  into  the  alloy. 
Or  they  may  be  produced  by  heating  the  mixed  oxides  in  a  graphite 
crucible  in  an  electric  furnace,  using  either  zircon  or  zirkelite  as  a 
source  of  zirconium  (486). 

For  use  as  a  scavenger  in  casting  steel  a  20  p.c.  ferro-zirconium  is 
recommended  in  an  amount  equal  to  1  p.c.  of  the  weight  of  steel 
treated. 

Furnace  Applications 

Mixed  with  good  conductors  zirconia  is  said  to  improve  furnace 
electrodes  (759).  On  account  of  its  low  conductivity  for  both  heat 
and  electricity  it  can  also  serve  as  an  insulating  material.  It  is  fur- 
ther used  to  replace  thorium  nitrate  for  coating  the  iridium  bar  and 
preventing  the  loss  of  iridium  in  the  Heraeus  furnace. 

The  oxide,  zirconia,  possesses  physical  and  chemical  properties 
which  make  it  available  for  a  variety  of  industrial  uses.  Among 
these  properties  are  its  high  melting  point  and  its  low  heat  con- 
ductivity. On  account  of  its  low  coefficient  of  expansion  it  with- 
stands sudden  changes  of  temperature.  Its  porosity  is  low,  so  that 
it  is  practically  impervious  to  liquids.  It  is  inactive  toward  most 
chemicals  and  is  scarcely  attacked  by  strong  acids  or  alkaline  fusion 
mixtures.  It  does  not,  however,  resist  the  action  of  hydrofluoric  acid 
and  fluorides.  Fused  bisulphates  also  act  upon  it  to  some  extent. 
It  is,  however,  quite  stable  in  the  presence  of  most  fluxes  and  slags. 

As  binding  material,  various  organic  substances,  such  as  starch, 
organic  acids,  glycerine,  tar,  etc.,  have  been  recommended;  also  mag- 
nesia, phosphates,  and  borates.  Since  the  native  zirconia  from  Brazil 
is  reasonably  pure,  it  may  be  used  direct  with  no  other  than  mechani- 
cal treatment.  Native  zirconia  begins  to  fuse  at  1800°.  For  use  in 
laboratories  and  chemical  manufacture  it  is  first  purified.  The  chief 
impurities  are  iron,  titanium,  and  silicon. 

Working  tests  show  that  zirconia  has  much  greater  life  duration 


130  ZIRCONIUM  AND  ITS  COMPOUNDS 

as  a  lining  for  furnaces  than  other  refractories.  In  Germany  experi- 
ments were  carried  out  in  a  closed  hearth  steel  furnace  and  it  was 
found  that  the  zirconia  lining  was  good  for  eight  months'  use  without 
renewal.  This  is  several  times  longer  than  the  usual  life.  Because 
of  the  low  thermal  conductivity  the  thickness  of  the  lining  could  be 
reduced  one-half,  a  two-inch  lining  being  equal  to  four  inches  of 
chamotte.  Furthermore,  there  was  a  saving  of  one-half  in  main- 
tenance costs.  In  casting  molds  it  shows  a  high  resistance  to  steel, 
copper,  brass,  and  bronzes. 

It  may  be  used  as  a  protective  coating  for  ordinary  firebrick  ex- 
posed to  the  action  of  acids  or  slags.  In  such  cases,  sodium  silicate 
serves  as  a  binding  material;  air-slaked  lime  may  also  be  added.  If 
it  is  desirable  to  increase  the  porosity  and  decrease  the  density  organic 
substances  or  volatile  salts  may  be  added  and  burned  out  in  the 
firing.  It  is  of  course  detrimental  to  use  a  binder  which  may  cause 
softening  at  comparatively  low  temperatures. 

Refractories 

As  a  refractory,  zirconia  has  also  been  used  in  making  crucibles, 
muffles,  pyrometer  tubes,  and  for  a  variety  of  chemical  wares.  Com- 
bustion tubes  made  of  it  are  said  to  be  gas-tight  up  to  1000°.  Cru- 
cibles and  combustion  tubes  of  zirconia  have  been  used  in  the  research 
laboratory  of  the  Royal  Berlin  Porcelain  Factory,  as  they  possess 
great  strength  and  also  conduct  electricity.  They  withstand  high 
temperatures  and  sudden  changes.  Zirconia  crucibles  have  been  used 
for  determining  the  melting  points  of  pure  iron,  tungsten  alloys,  and 
platinum.  Such  ware  can  be  plunged  in  water  while  red  hot  without 
injury.  (For  its  use  as  a  refractory  see  13,  14,  278,  588,  589,  605,  624, 
625,  626,  178,  290,  572.) 

Enamels 

Zirconia  is  also  used  as  an  opacifying  agent  in  enamels  and  a 
clouding  agent  in  glass  as  a  substitute  for  the  costly  stannic  oxide  and 
the  poisonous  compounds  of  antimony  and  arsenic.  For  this  purpose 
it  should  be  quite  free  from  iron,  and  a  number  of  processes  have  been 
worked  out  and  some  patented.  General  references  follow  (266,  267, 
288,  336,  413,  430,  431,  432,  166,  592,  658,  675,  802,  762).  The  in- 
creasing demand  for  tin  for  other  purposes  and  the  limited  supply 
may  render  this  substitution  necessary.  According  to  some  author- 


TECHNICAL  APPLICATIONS  OF  ZIRCONIUM         131 

ities,  the  zirconia  has  less  covering  power  than  stannic  oxide.  For 
cheaper  ware  native  zirconia  may  be  used,  or  ground  zircon  which 
has  been  treated  with  hydrochloric  acid,  then  caustic  soda,  and  finally 
leached  with  acidulated  water.  This  would  only  partially  remove  the 
iron  present. 

Glass 

The  use  of  zirconia  as  a  clouding  agent  for  glass  has  been  men- 
tioned above.  A  thorough  comparison  with  stannic  oxide  in  this 
application  apparently  has  not  been  worked  out.  The  addition  of  a 
small  amount  of  zirconia  to  "vitreosil"  or  silica  glass  is  said  to  in- 
crease the  tensile  strength  and  resistance  to  bending  or  breaking,  and 
to  diminish  the  tendency  to  devitrification.  The  temperature  at  which 
the  ware  softens  is  practically  unchanged.  The  appearance  is  not 
improved  (3,  90,  494,  655,  702,  823). 

Textile  Applications 

Zirconium  salts,  as  the  hydrated  sulphate  or  the  acetate,  have 
been  used  as  a  weighting  filler  for  silk  (429,  594,  678).  The  weight 
may  be  increased  up  to  50  p.c.  Stannic  salts  are  ordinarily  employed 
for  this  purpose. 

Various  zirconium  compounds  are  also  used  as  mordants  in  dyeing 
(26,  642,  813)  and  in  the  preparation  of  lac  dyes  (642).  Zircon  white 
(799)  is  used  as  a  pigment,  having  good  covering  powers  and  being 
unaffected  by  chemical  agents  (84).  A  patent  has  also  been  issued 
for  the  preparation  of  a  zirconyl  tannate  (573) . 

It  may  also  find  a  use  as  substitute  for  sodium  tungstate  or  stan- 
nate  in  rendering  cloth  non-inflammable. 

Colloidal  Applications 

The  colloidal  properties  of  the  hydroxide  have  been  compared 
with  those  of  other  hydroxides  and  its  use  suggested  in  the  purifica- 
tion of  water  (67,  68,  71). 

Medicinal 

As  "Kontrastin"  it  may  be  substituted  for  bismuthyl  nitrate  as  a 
lining  substance  for  the  stomach,  etc.,  in  X-ray  observations  and 
radiographs.  It  has  the  advantage  of  being  non-poisonous  (803). 
This  has  been  patented. 


132  ZIRCONIUM  AND  ITS  COMPOUNDS 

Abrasive 

The  carbide  has  been  recommended  as  a  polishing  agent,  abrasive, 
and  for  glass  cutting  (798,  801). 

Chlorinating  Agent 

Willgerodt  (816)  has  suggested  the  use  of  the  tetrachloride  as  a 
chlorinating  agent. 


Chapter  XII 
Patents 

1914.  Arnold  (11).    U.  S.  Patent  1,121,890. 

Utensils  made  of  zirconia.  The  oxide  is  subjected  to  a  high 
pressure.  After  withdrawing  the  pressure  the  substance  is  turned 
into  a  paste  by  means  of  a  suitable  fluid  (water,  alcohol,  or  the 
like) ,  cast  in  molds,  dried,  and  burned.  The  articles  do  not  crack 
nor  fissure.  They  may  be  glazed  with  titanium  oxide,  alumina, 
or  silica.  Similar  articles  made  of  thoria  or  the  rare  earths  may 
be  glazed  with  zirconia.  The  melting  point  of  the  glaze  may  be 
so  arranged  by  mixing  such  oxides  as  to  be  a  few  hundred  degrees 
over  the  highest  temperature  to  which  the  article  is  to  be  exposed. 
The  glaze  is  dried  and  burned  on  in  a  second  heating. 

1915.  Askenasy  (12).    U.  S.  Patent  1,158,769.    C.  A.  10,  255. 
Method  of  producing  zirconia  free  from  iron.    This  consists 

in  heating  the  zirconium  salt  of  a  mineral  acid  (containing  such 
impurities)   under  pressure  to  a  temperature  above  the  boiling 
point.    Zirconium  hydroxide  separates  out  in  an  easily-filtered 
form  and  the  impurities  are  left  in  the  acid  solution. 
1909.    Badische  Anilin  u.   Sodafabrik    (17).    Ger.   Patent  237,436. 

C.  A.  6,  1507. 

This  patent  refers  to  the  preparation  of  zirconium  nitride  and 
its  purification  by  treating  with  acid  or  oxidizing  agents. 
1920.    Barton  (28).    U.  S.  Patent  1,342,084.    C.  A.  14,  2140. 

Zirconium  cyanonitride.  Ore  mixed  with  about  20  per  cent 
of  coke  is  heated  in  an  electric  furnace  (with  a  nitrogen-bearing 
gas?).  This  yields  a  product  containing  Zr  82-84  per  cent,  C  3-5 
per  cent,  and  N  8-10  per  cent.  Cold  5  per  cent  H2S04  may  be 
used  to  remove  excess  of  iron.  The  product  is  golden  yellow  to 
bronze  in  color  and  has  a  specific  gravity  of  5.95-6.35. 
1920.  Barton  (29).  U.  S.  Patent  1,351,091.  C.  A.  14,  3301. 

Zirconium  oxide.  This  oxide  may  be  produced  from  baddeley- 
jte  pr  zircon  by  melting  with  carbonaceous  material,  such  as  coke, 

133 


134  ZIRCONIUM  AND  ITS  COMPOUNDS 

to  form  zirconium  cyanonitride  and  the  resulting  product  then 
heated  with  salt  cake  or  niter  cake. 
1914.    Bohm  (85).    U.  S.  Patent  1,099,110.    C.  A.  8,  2653. 

This  describes  the  fusion  of  zirconia  in  caustic  alkali  by  means 
of  an  electric  current.  The  zirconia  is  mixed  with  caustic  alkali, 
which  acts  as  an  initial  conductor  and  is  later  volatilized. 

1914.  Bosch  and  Mittasch  (91).    U.  S.  Patent  1,102,715.      C.  A.  8, 

3353. 

Purification  of  the  nitride.  Heat  with  air  at  700°  to  burn  out 
any  carbon.  Treat  the  residue  with  H2S04  or  HC1  or  FeCl3 
solution  to  decompose  other  impurities  without  decomposing  the 
nitride.  K2Cr207,  Mn02,  and  a  flux  may  also  be  used  in  oxidiz- 
ing the  impurities. 
1919.  British  Thomson-Houston  Co.  (103).  Brit.  Patent  139,247. 

C.  A.  14,  1960. 

Alumino-thermic  extraction  of  zirconium.  Finely  divided 
Al  (80-200  mesh)  mixed  with  10  per  cent  fine  flaky  Al  (60-200 
mesh)  is  briquetted  with  zirkite,  Na2Si03  serving  as  binder.  The 
slag  may  be  used  as  an  abrasive. 

1915.  Brown  and  Cooper  (107).    U.  S.  Patent  1,151,160. 
Production  of  ferro-zirconium.    This  alloy  contains  40-90  p.c. 

of  zirconium.  It  may  also  have  60-90  p.c.  of  zirconium  along 
with  an  iron-group  metal.  It  is  malleable  and  ductile.  The 
oxides  of  zirconium  and  iron  (and  titanium)  are  mixed  with 
aluminum  and  the  mixture  ignited. 

1916.  Campbell  and  Carney  (114).    U.  S.  Patent  1,182,880.    C.  A. 

10,  1918. 

Separation  of  zirconium  and  thorium  from  the  rare  earths. 
The  pyrophosphates  of  zirconium  and  thorium  are  insoluble  in 
dilute  acids.  The  pyrophosphates  of  the  rare  earths,  except  eerie 
salts,  are  soluble.  Reduction  by  means  of  H2S03  renders  the 
latter  soluble  also.  Zirconium  is  then  separated  from  thorium 
by  the  solubility  of  the  oxalate  in  oxalic  acid. 

1917.  Cooper  (150).     Can.  Patent  179,121.     C.  A.  11,  3234. 
Production  of  an  alloy  for  cutting  tools  containing  8-15  p.c.  of 

zirconium  with  50  p.c.  or  more  of  nickel.     It  is  free  from  iron  or 
carbon  and  will  not  burn  when  cutting  at  high  speed  or  grinding. 
The  wear  is  small  and  the  tool  remains  white. 
1917.     Cooper  (151).    Brit.  Patent  112,259.    C.  A.  12,  1286. 

Production  of  an  alloy  for  cutting  tools,  electrical  resistance, 


PATENTS  135 

etc.  It  contains  2-40  p.c.  of  zirconium,  the  remainder  being  nickel 
or  cobalt.  One  or  more  metals  of  the  chromium  group  may  be 
added.  The  alloy  may  also  contain  up  to  35  p.c.  of  molybdenum; 
up  to  25  p.c.  of  zirconium,  the  remainder  being  nickel  or  cobalt; 
or  up  to  25  p.c.  of  tungsten  and  the  remainder  nickel  and  zir- 
conium. These  alloys  are  made  by  the  thermo-aluminic  method, 
the  reactions  taking  place  between  mixtures  of  the  oxides  of 
nickel,  zirconium,  etc.,  or  their  ores  and  aluminum. 

1918.     Cooper  (152).     Can.  Patent  185,436.     C.  A.  12,  1762. 

Production  of  an  alloy  containing  zirconium,  nickel,  aluminum, 
and  silicon,  which  is  especially  adapted  to  cutting.  The  addition 
of  silicon  greatly  increases  the  hardness.  Zirconium  modifies  the 
physical  and  structural  characteristics.  A  scleroscopic  hardness 
of  65-75  is  easily  reached.  Tungsten  may  be  added. 

1920.     Cooper  (153).    U.  S.  Patent  1,350,359.     C.  A.  14,  3219. 

Alloy  for  cutting  tools.  This  may  be  used  for  high  speed 
cutting  tools  and  is  composed  of  Ni  76.2  p.c.,  Zr  4.8  p.c.,  Al  2.0 
p.c.,  Si  5.9  p.c.,  W  3.8  p.c.,  Fe  6.8  p.c.,  and  C  0.29  p.c. 

1920.  Cyclops  Steel  Co.  (159).  Brit.  Patent  151,981.  C.  A.  15,  667. 
Corrosion-resisting  steel  alloy.  This  contains  Fe  of  low  car- 
bon content,  Si  and  Zr  or  other  metal  of  the  C  group.  The  per- 
centage of  Si  and  Zr  together  is  preferably  about  2.  Cr  or  Cr, 
Ni,  and  Mn  may  be  added,  the  percentage  of  Cr  being  about 
3-7  and  of  Ni  about  5-20.  In  some  cases  about  0.3  p.c.  Cu  may 
be  added. 

1920.     Dantsizen  (166).    U.  S.  Patent  1,343,040.    C.  A.  U,  2403. 

Porcelain  containing  zirconium  oxide.  Zr02  to  the  amount  of 
about  15  p.c.  is  used  in  porcelain  to  improve  its  strength  and 
electrical  resistance  at  high  temperatures.  The  porcelain  may 
be  formed  of  clay,  45;  feldspar,  35;  and  zirconia,  15  parts. 

1914.    Dennis  (175).    U.  S.  Patent  1,115,513.     C.  A.  9,  27. 

This  describes  a  method  for  separating  zirconium  from  the  rare 
earths  by  electrolysis.  The  aqueous  solution  of  the  nitrates  is 
subjected  to  the  action  of  an  electric  current  while  maintaining 
the  cathode  surface  substantially  free  from  an  adherent  deposit. 
The  current  is  at  or  above  the  lowest  decomposition  voltage  of 
the  first  product  desired.  The  deposition  is  fractional.  The 
separate  portions  are  removed  as  formed  and  the  remainder  is 
subjected  again  to  the  action  of  the  current.  The  mercury 


136  ZIRCONIUM  AND  ITS  COMPOUNDS 

cathode  is  kept  clean  by  forcing  air  through  the  mercury  so  as 
to  agitate  it  and  prevent  any  formation  on  the  surface. 
1913.    Ehrich,    Gratz,    and   Podszus    (207).     Ger.    Patent    289,063. 

C.  A.  10,  2438. 

Production  of  filaments.  Pure  zirconium  is  ground  to  a  fine 
powder.  It  is  then  worked  into  an  emulsion  with  a  liquid,  such 
as  C6H6,  CS2,  etc.,  and  formed  in  filaments  by  pressure.  These 
are  heated  by  electricity  in  a  non-oxidizing  atmosphere  close  to 
the  melting  point  and  this  temperature  is  maintained  for  a  long 
time. 

1918.  Elektro-Osmose    Gesellschaft    (208).     Brit.    Patent    113,777. 

C.  A.  12,  1415. 

Use  in  enamels.     Colloidal  zirconium  hydroxide  as  hydrosol  is 
applied  as  a  coating,  dried,  and  fired  at  a  temperature  below  the 
melting  point.    A  small  amount  of  water-glass  may  be  added  if 
desired. 
1902.    Escales  (213).     Ger.  Patent  145,820.     C.  B.  1903,  II,  1155. 

A  method  of  preparing  metallic  zirconium  or  its  alloys.  This 
involves  the  use  of  rare-earth  metals  or  mixtures  of  their  alloys 
with  magnesium  or  aluminum.  Carbides  or  phosphides  of  these 
metals  may  also  be  used,  or  mixtures  of  these,  such  as  may  be 
obtained  by  the  electric  melting  of  the  phosphates,  etc.,  mixed 
with  carbon.  The  reduction  process  is  endothermic. 

1919.  Eyer  (215).    U.  S.  Patent  1,314,861.     C.  A.  18,  2748. 

A  clouding  composition  for  enamels.  Zirconia  is  apt  to  pro- 
duce spotted  enamels  and  also  they  may  become  dull  or  tarnished 
on  firing.  Ordinary  zirconium  borate  is  free  from  these  defects 
but  has  poor  covering  capacity.  A  highly  basic  zirconyl  borate, 
as  Zr02 .  2B203  -f-  4Zr02,  has  much  greater  covering  capacity  and 
is  free  from  the  defects  mentioned.  The  process  consists  in  fusing 
together  7  parts  of  raw  zirconia,  about  3  parts  of  B203,  about  2 
parts  of  cryolite,  and  5  parts  of  NaN03,  allowing  the  mass  to  cool 
and  powdering  it. 

1908.    General  Electric  Co.   (239).    Brit.  Patent  5,415.     Soc.  Chem. 
Ind.  28,  83. 

Filaments  for  incandescent  lamps.  Filaments  or  other  con- 
ductors are  made  from  zirconium  oxalate  with  just  enough  zir- 
conium on  heating  to  the  necessary  temperature  without  leaving 
any  residual  carbon.  No  binding  material  is  necessary,  since  the 
oxalate  forms  a  tenacious  paste  which  can  be  squirted.  The 


PATENTS  137 

oxalate  may  be  prepared  by  precipitating  a  hot  zirconium  nitrate 
solution  with  ammonium  oxalate.  It  resembles  starch  paste. 
The  heating  may  also  be  applied  to  the  production  of  alloys  of 
zirconium. 

1917.    Glazebrook,  Rosenhain  and  Rodd  (247).    Brit.  Patent  112,973. 

C.  A.  12,  1111. 

This  covers  a  basic  zirconyl  sulphate  and  a  basic  zirconyl 
chloride.  The  sulphate  is  obtained  by  adding  caustic  alkali, 
such  as  NH4OH  or  NaOH,  to  an  acid  solution  of  Zr(S04)2  until 
a  permanent  precipitate  begins  to  form  and  then  allowing  the 
precipitation  to  proceed  of  itself.  This  basic  sulphate  may  be 
converted  into  tha  oxide  by  ignition.  Likewise  a  basic  zirconyl 
chloride  Zr508Cl4.22H20  may  be  prepared,  dissolved  in  water, 
H2S04  added  and  a  sulphate  5Zr02.2S03.14H20  formed. 

1920.     Gordon  (250).    U.  S.  Patent  1,340,888.     C.  A.  14,  2242. 

Preparation  of  Zr02  from  ore.  Ore  is  fused  with  3-4  times  its 
weight  of  Na20,  NaOH,  Na2C03  or  CaO  and  3-4  times  its  weight 
of  NaCl  or  CaCl2.  Fusion  at  1000°-2000°  for  30-60  minutes, 
poured,  cooled,  pulverized.  Si02  separated  with  H2S04,  filtered, 
precipitated  as  Zr(OH)4  and  other  bases  by  NH4OH  or  other 
alkali. 

1917.    Grenagle  (258).    U.  S.  Patent  1,248,648.    C.  A.  18,  361. 

Ferro-zirconium  alloys.  The  object  is  to  produce  an  alloy  of 
zirconium,  which,  because  of  its  selective  radiation,  will  be  use- 
ful for  filaments  in  electric  lamps,  and  in  the  manufacture  of 
transformer  elements.  The  process  is  one  of  co-reduction  of 
compounds  containing  zirconium  and  iron,  best  in  the  presence 
of  a  titaniferous  compound.  This  reduction  may  be  brought 
about  by  aluminum.  Thus  3Zr02  +  3Fe203  +  5A12  = 
3ZrFe2  +  5A1203.  This  reaction  may  be  carried  out  by  heating 
the  mixed  oxides  with  aluminum  in  a  graphite  crucible  with  the 
electric  current  or  oxy-acetylene  flame. 

1920.     Grenagle  (259).    U.  S.  Patent  1,334,089.     C.  A.  14,  1266. 

Zr-Nb-Ta  alloy.  Formed  by  heating  the  mixed  oxides  in  an 
electric  furnace.  It  contains  Zr  6.8  p.c.,  Nb  53.5  p.c.,  Ta  39.7 
p.c.  It  is  not  attacked  by  acids  or  alkaline  solutions,  does  not 
oxidize  or  vaporize  at  white  heat,  and  combines  with  C  to  form 
carbides  which  are  hard  and  brittle.  The  alloy  is  malleable,  duc- 
tile, and  somewhat  resembles  Pt  but  is  slightly  yellowish. 

1904.    Guertler  (269).    Ger.  Patent  182,200.    C.  B.  1907,  I,  1518. 


138  ZIRCONIUM  AND  ITS  COMPOUNDS 

A  method  of  changing  difficultly  crystallizable  substances  into 
crystalline  form.  The  compounds  or  mixtures  are  dissolved  in 
fused  alkaline  metaborates  (e.g.,  NaB02)  and  this  solvent  driven 
off  by  heat,  which  is  readily  done  at  850°-950°  in  a  platinum 
crucible.  LiB02  is  volatilized  in  8  hours,  NaB02  in  4  hours,  and 
KB02  in  1  hour.  Zircon  can  be  crystallized  in  this  way. 

1909.     Gustrow   (271).     Ger.  Patent  189,364. 

This  refers  to  the  use  of  zirconia  as  an  opacifier  in  enamels. 

1912.    Hansen  (283).    U.  S.  Patent  1,026,392.     C.  A.  6,  1882. 

Improvement  in  incandescent  lamp  filaments.  This  consists 
in  forming  threads  made  of  refractory  powder  held  together  by  a 
binder  composed  essentially  of  gelatinous  zirconium  oxalate,  de- 
composable into  a  refractory  oxide,  and  heating  said  threads  in 
an  inert  environment  to  convert  the  oxalate  into  oxide  and  to 
consolidate  and  sinter  the  refractory  metal. 

1914.    Hansen  (284).    U.  S.  Patent  1,084,629.     C.  A.  8,  871. 

Improvements  in  zirconium  lamp  filaments.  The  process  con- 
sists in  mixing  carbon  with  gelatinous  zirconium  oxalate,  shaping 
the  mixture  into  threads,  then  heating  in  an  inert  and  rarefied 
atmosphere  to  produce  coherent  conductors  of  pure  zirconium. 

1912.  Havas  (310).    Ger.  Patent  262,009.    C.  A.  7,  3650. 

This  refers  to  the  production  of  iron-free  zirconia  for  enamels. 
A  weak  hydrochloric  acid  solution  of  a  zirconium  salt  is  heated 
in  a  closed  vessel  to  temperatures  above  the  boiling  point  (at 
ordinary  pressure).  Zirconium  hydroxide  separates  out,  is  fil- 
tered, centrifuged,  and  washed.  This  is  snow-white  on  ignition. 
Other  acids  besides  hydrochloric  may  be  used. 

1913.  Havas  (311).    Brit.  Patent  9,153.     C.  A.  8,  3355. 

This  is  apparently  the  same  as  preceding,  only  more  detailed. 
The  temperature  to  which  the  acid  zirconyl  chloride  solution  is 
heated  is  given  as  200°. 
1905.    Heraeus.(318).     Ger.  Patents  156,776  and  179,570. 

These  refer  to  the  making  of  chemical  apparatus  out  of  zir- 
conia. 

1914.  Herzfeld   (330).     Ger.  Patent  290,878.    Soc.  Chem.  Ind.  35, 

634. 

A  process  for  obtaining  pure  Zr02  from  zirkite.  The  ore  with 
excess  of  lime  and  carbon  is  heated  short  of  complete  reduction 
of  the  lime.  The  product  is  then  treated  with  hydrochloric  acid, 


PATENTS  139 

the  silica  removed,  and  the  zirconyl  chloride  purified.    Calcium 
carbide  may  be  used  in  place  of  carbon. 

1920.    Hisamoto   (341).    U.  S.  Patent  1,345,441.    C.  A.  14,  2687. 

Drawing  filaments.  Zr  is  surrounded  by  Zr02,  enclosed  in  a 
tube  of  metal  as  Ni,  and  contents  drawn  to  a  filament.  The  tube 
and  oxide  are  dissolved  away  with  acid. 

1920.     Hutchins  (364).    U.  S.  Patent  1,362,316.    C.  A.  15,  583. 

Refractory  material.  Such  a  material  suitable  for  furnace  lin- 
ings, crucibles,  or  muffles  is  formed  of  a  burnt  mixture  of  zirconia 
and  alumina. 

1920.  Hutchins  (365).    U.  S.  Patent  1,362,316.    C.  A.  15,  583. 
Refractory  material.    A  mixture  of  burnt  zirconia  and  chro- 

mite  is  used  as  a  refractory  material  for  furnace  construction  and 
similar  uses. 

1914.  Jost  and  Plocker  (380).  Ger.  Patent  285,981.  C.  A.  10,  1087. 
Preparation  of  the  silicide,  oxide,  and  salts.  Pulverized  zircon 
is  mixed  with  1  1/9  times  its  weight  of  coal  and  heated  to  white- 
ness. The  silicide  is  formed  and  carbon  dioxide  escapes.  The 
resulting  mass  is  treated  with  dilute  mineral  acid  and  filtered 
away  from  the  carbon.  The  salt  is  thus  freed  from  silica  and  on 
ignition  the  oxide  is  obtained.  It  is  useful  for  enamels. 

1921.  Kaiser  (381).    Can.  Patent  207,290.    C.  A.  15,  667. 

Alloys  having  high  melting  point  and  ductile  properties  are 
produced  from  such  metals  as  Cr,  W,  V,  Th,  Zr,  and  Ru  by  add- 
ing one  metal  to  another,  which  is  used  as  a  base,  and  adding  a 
small  amount  of  a  second  metal,  which  has  a  catalytic  action, 
before  sintering  the  mixture. 

1887.    Keeport  (385).    Ger.  Patent  43,231.    Ber.  deutsch.  chem.  Ges. 
21  c,  458. 

Zirconium  is  described  as  having  a  great  affinity  for  gold, 
platinum,  etc.  Zirconiferous  ores  are  added  to  the  material  car- 
rying the  precious  metals  and  the  mixture  is  treated  with  a  sol- 
vent. The  undissolved  material  is  separated  and  the  precious 
metals  precipitated.  (This  is  seemingly  meaningless.) 
1913.  Knofler  (397).  Ger.  Patent  285,934.  C.  A.  10,  1087. 

This  refers  to  the  manufacture  of  refractory  vessels.  Pure  zir- 
conia mixed  with  some  water  is  shaped  by  high  pressure  into 
suitable  forms.  Upon  subsequent  burning  in  furnaces  at  1400°- 
1600°  the  articles  acquire  the  requisite  solidity  and  hardness  with 
contraction.  There  is  no  sintering.  The  vessels  may  be  heated 


140  ZIRCONIUM  AND  ITS  COMPOUNDS 

"to  2000°  and  above  for  a  long  time  without  fusion.    Thoria  and 
the  rare  earths  may  be  mixed  with  the  zirconia. 

1913.    Knofler  (398).     Ger.  Patent  287,554.     C.  A.  10,  2134. 

This  is  an  addition  to  the  preceding  patent.  Zirconia,  or  a 
mixture  with  thoria,  without  binding  material  is  subjected  to  high 
pressure.  After  relieving  the  pressure  the  product  is  finely  ground 
and  then  stirred  with  water  or  alcohol  and  poured  into  the  forms, 
dried,  and  burned.  The  articles  are  readily  removable  from  the 
forms.  There  are  no  cracks  on  drying  or  burning.  The  vessels 
are  tight  and  not  easily  fractured. 

1907.    Kuzel  (418).    U.  S.  Patent  871,599.    C.  A.  1,  1930. 

A  method  of  converting  elements  into  the  colloidal  state.  This 
consists  in  first  comminuting  the  zirconium  and  then  treating  the 
same  under  heat  and  agitation  alternately  with  dilute  solutions 
of  an  acid  character,  and  then  dilute  solutions  of  a  non-acid 
character,  and  between  such  treatments  washing  with  pure  in- 
hibition liquid.  The  acid  solutions  may  be  organic  from  0.5-20 
p.c.,  or  mineral  acids  or  salts  having  an  acid  reaction.  The  basic 
may  be  0.5-10  p.c.  caustic  alkali  solutions,  ammonia,  or  organic 
bases. 

1907.  Kuzel  (419).    Ger.  Patent  204,496.    C.  A.  3,  881. 

A  process  for  making  alloys  of  definite  composition  and  objects 
therefrom.  One  constituent  only  need  be  in  colloidal  form  (i.e., 
zirconium)  and  as  many  others  as  desired  in  the  form  of  crystal- 
loids, such  as  salts,  oxides,  hydroxides,  acid  salts,  and  halogen 
compounds.  These  latter  are  combined  with  the  colloid  by  suit- 
able means,  such  as  precipitation  of  the  colloid  with  an  electro- 
lyte until  a  plastic  mass.  This  method  is  applicable  in  the 
manufacture  of  filaments. 

1908.  Kuzel  (420).    U.  S.  Patent  899,875.     C.  A.  3,  288. 

A  process  for  peptizing  coagulated  colloids  of  refractory  ele- 
ments free  from  carbon.  This  consists  in  treating  such  colloids 
with  solutions  of  alkaline  reaction  and  stopping  such  treatment 
before  pectization  begins.  Zirconium  is  very  easily  peptized. 
The  gel  is  peptized  by  treating  with  a  small  quantity  of  an 
alkaline  solution — caustic  or  carbonate.  Such  peptized  col- 
loids have  in  a  concentrated  form  a  high  agglomerative  power 
for  dry  powders  of  any  kind,  as,  for  instance,  metal  powders, 
giving  a  plastic  mass  which  can  be  formed  in  threads,  etc.  These 


PATENTS  141 

are  dried  and  heated  to  a  temperature  exceeding  the  melting  point. 
The  colloid  is  converted  into  the  metallic  state.  If  powdered 
lead  be  added  and  the  plastic  mass  molded  projectiles  of  high 
density  and  great  toughness  are  obtained. 

1909.  Kuzel  (421).    U.  S.  Patent  914,354.    C.  A.  3,  228. 
Filaments  for  electric  incandescent  lamps.    This  consists  of  an 

alloy  of  antimony  with  such  metals  as  zirconium.  According  to 
this  method,  filaments  are  made  from  plastic  masses  consisting 
of  colloidal  zirconium  with  or  without  the  addition  of  the  pow- 
dered metal  and  with  or  without  the  addition  of  the  colloidal 
hydroxide.  Antimony  is  incorporated  into  the  plastic  mass  in  a 
colloidal  or  finely-divided  state,  or,  instead  of  antimony,  sulphur 
or  oxygen  compounds  of  antimony  may  be  used.  This  plastic 
mass  is  brought  into  the  desired  form,  dried,  and  heated  to  a  white 
heat.  An  alloy  is  thus  obtained  with  antimony  the  presence  of 
which  gives  a  notable  increase  in  the  electrical  resistance. 

1910.  Kuzel  (422) .    U.  S.  Patent  969,064.    C.  A.  4,  2908. 

A  process  for  manufacturing  articles  with  the  use  of  colloids. 
A  pasty  colloid,  preferably  a  peptized  colloid,  of  lead  or  pul- 
verulent lead  to  which  finely-divided  zirconium  has  been  added 
is  brought  to  the  desired  consistency  and  molded  under  high  pres- 
sure. The  articles  are  then  dried  and  gradually  raised  to  a  tem- 
perature below  the  melting  point  of  the  ingredients  in  the  absence 
of  active  gases. 
1910.  Kuzel  (423).  U.  S.  Patent  969,109.  C.  A.  4,  2909. 

Solder  for  electrically  connecting  filaments  of  electrical  incan- 
descent lamps.    The  carbide  of  aluminum,  to  which  may  be  added 
the  carbide  of  zirconium  to  raise  the  melting  temperature,  is  used. 
1914.    Kuzel  and  Wedekind  (424).    U.  S.  Patent  1,088,909.    C.  A. 

8,  1408. 

Preparation  of  pure  zirconium.  Mix  Zr02  and  finely  divided 
calcium.  Enclose  in  a  steel  bomb  and  exhaust.  Heat  with  a 
strong  flame  till  reaction  begins,  then  heat  of  reaction  is  suffi- 
cient. Cool  gradually,  finally  in  ice  water.  Treat  contents  with 
water,  then  dilute  acid,  to  remove  CaO.  Grind,  wash,  and  dry 
residue.  To  drive  off  gases  completely,  heat  in  vacuo  to  1000°. 
Zirconium  about  96  p.c.  pure. 
1912.  Landau,  Kreidl,  Heller  and  Co.  (432).  Ger.  Patent  294,202. 

C.  A.  12,  413. 
Use  as  a  clouding  agent  for  enamels.    Alkali  zirconium  com- 


142  ZIRCONIUM  AND  ITS  COMPOUNDS 

pounds  in  hydrous  form  are  used.  The  alkali  content  should  lie 
between  2  and  7  p.c.  The  water  content  depends  upon  that  of 
the  alkali.  The  lower  the  alkali,  the  larger  the  amount  of  com- 
bined water.  The  water  is  only  partially  removed. 

1913.  Landau,  Kreidl,  Heller  and  Co.  (429).    Ger.  Patent  258,638. 

C.  B.  1913,  I,  1629. 

Use  for  weighting  silk.  This  substitutes  salts  of  zirconium  for 
tin  salts  in  weighting  silk.  It  is  carried  out  by  the  usual  methods 
of  practice  with  fixing  baths. 

1914.  Landau,  Kreidl,  Heller  and  Co.  (431).     Ger.  Patents  283,504, 

281,571.     C.  B.  1915,  I,  280. 

These  refer  to  the  use  of  zirconium  compounds  in  white 
enamels. 

1909.  Lesmiiller    (442).     Ger.    Patent    231,002.     Chem.    Ztg.    Rep. 

1911,  108. 

Use  for  making  sound  castings.  Zirconium  in  metallic  form 
is  added  to  the  metal  to  be  cast  to  insure  a  casting  free  from 
imperfections. 

1910.  Lesmuller    (443).     Ger.    Patent    218,316.     Chem.    Ztg.    Rep. 

1910,  91. 

Use  as  a  clouding  agent.  Borax  or  boron  trioxide  melted  with 
zirconia  gives  a  colorless  glass  if  enough  of  the  borax  is  used. 
The  solution  of  the  zirconia  is  aided  by  the  presence  of  silica. 
If  cooled  under  steam  or  acid  vapors,  cloudings  caused  by  the 
separation  of  double  compounds  with  B203  are  given.  By  slow 
cooling  the  separation  is  avoided  and  amorphous,  homogeneous 
masses  are  obtained.  The  enamel  is  stable  towards  acids  and 
alkalies. 
1914.  Leuchs  (444).  Ger.  Patent  285,344.  C.  A.  10,  375. 

This  refers  to  the  purifying  of  zirconia.  Add  H2S04  to  a  solu- 
tion of  the  chloride  in  the  proportion  7Zr02:4H2S04  and  boil. 
Without  applying  pressure  a  readily  filtered,  crystalline,  iron- 
free  precipitate  of  basic  zirconyl  sulphate  (ZrO2.3S03.14H20)  is 
obtained.  Precipitate  with  ammonia  or  caustic  alkali,  dry,  and 
pulverize.  The  product  is  especially  suitable  for  enamels. 
1918.  Loveman  (454).  U.  S.  Patent  1,261,948. 

This  is  a  process  for  purifying  zirconia  ores.  Alumina  and 
silica  are  removed  by  fusion  with  Na2C03  added  in  a  ratio  greater 
than  1  :  6  and  leaching  out  the  aluminate  and  silicate.  The 
residue  is  then  treated  with  dilute  HC1,  washed,  and  ignited. 


PATENTS  143 

1896.    Muller-Jacobs   (513).    U.  S.  Patent  558,197.    Ber.  d.  chem. 

Ges.  29,  d,  448. 

A  method  for  manufacturing  tannate  of  zirconium.  This  con- 
sists in  dissolving  a  salt  of  zirconium  in  boiling  water  and  slowly 
adding  a  saturated  solution  of  tannic  acid  heated  to  boiling,  wash- 
ing and  filtering  the  precipitate,  and  drying  at  a  suitable  tem- 
perature— not  exceeding  100°.  This  may  be  used  to  decolorize 
solutions,  to  make  lac  dyes,  to  prevent  or  retard  fermentation, 
and  as  an  antiseptic. 
1914.  North  (524).  Ger.  Patent  288,969.  C.  A.  10,  2461. 

A  method  of  recovering  the  valuable  constituents  in  zirconium 
ores.  The  ore  is  added  to  molten,  high-carbon  iron  to  the  com- 
plete saturation  of  the  metal  and  the  metallic  solvent,  then  re- 
moved by  dissolving  in  acids  or  burning  off.  In  using  ground 
ore  (Zr02  85.7  p.c.,  Si02  7.4  p.c.,  Fe203  4.1  p.c.,  and  Ti02  0.6  p.c.) 
the  residual  mass  has  a  very  high  melting  point  and  approaches 
zirconium  in  properties. 
1920.  North  and  Loosli  (525).  Brit.  Patent  155,299.  C.  A.  15, 

1108. 

Preparation  of  zirconium.  Zirconium  ore  or  oxide  is  reduced 
by  mixing  it  with  the  theoretical  amount  of  carbon  and  heating 
the  mixture  under  increased  pressure  in  an  electric  furnace.  The 
current  may  pass  through  the  charge  itself  or  a  conductive  carbon 
core  may  be  used. 
1918.  Norton  Co.  (527).  Brit.  Patents  113,958  and  113,959.  C.  A. 

12,  1442. 

Production  of  an  abrasive.  A  crystalline  product  is  obtained 
by  fusing  alumina  and  zirconia  in  an  electric  furnace,  the  pro- 
portion of  zirconia  ranging  up  to  equi-molecular.  Bauxite  is 
calcined  and  mixed  with  zirconia.  If  desired,  a  small  percentage 
of  coal  is  added  to  reduce  the  iron  oxide  and  silica.  Powdered 
zircon  may  be  used.  The  product,  together  with  a  binding  ma- 
terial, may  be  formed  into  wheels,  etc. 
1920.  Petinot  (541).  U.  S.  Patent  1,335,982.  C.  A.  14,  1519. 

Alloy  of  zirconium  and  lead.  This  is  formed  by  melting  a 
mixture  of  Zr02  and  CaO  in  such  proportions  as  to  prepare 
CaZrO3,  adding  sufficient  carbon  to  reduce  the  Zr02  to  Zr  and 
to  form  CaC2,  and  then  charging  the  resulting  material  into 
molten  Pb. 


144  ZIRCONIUM  AND  ITS  COMPOUNDS 

1920.    Petinot  (542).    U.  S.  Patent  1,335,983.     C.  A.  14,  1920. 

Ferro-alloys  containing  zirconium  carbide.  These  are  formed 
by  smelting  a  mixture  of  Zr  ore,  Fe,  and  C  and  rapidly  cooling 
to  prevent  the  formation  of  graphite.  They  contain  zirconium 
carbide  or  a  double  carbide  of  Zr  and  Fe. 

1919.  Pugh   (570).    U.  S.  Patent  1,316,107.     Chem.  Met.  Eng.  21, 

742. 

A  process  for  preparing  basic  zirconyl  sulphate.  Sulphuric 
acid  is  added  to  an  acid  solution  of  zirconyl  chloride  in  the 
proportion  3H2S04  :  5Zr02  and  heated.  The  product  is 
5Zr02.3S03.13H20. 

1920.  Rare   Metals   Reduction    Co.    (582).    Brit.    Patent    138,348. 

C.  A.  14,  1643. 

Alloys  for  lamp  filaments,  electrodes,  etc.  These  non-corrod- 
ing alloys  include  Zr  and  Fe  —  Zr  40-90  p.c.  or  as  low  as  8.43 
p.c.  Ti,  Al,  Nb,  Ta  may  be  added  and  Fe  replaced  by  Ni,  Co, 
or  Mn.  The  alloys  are  made  by  reduction  of  the  metals,  pref- 
erably in  the  presence  of  a  titanium  compound.  All  may  be  used 
in  the  reduction. 
1915.  Rietz  (591).  Brit.  Patent  4,457.  Soc.  Chem.  Ind.  35,  532. 

Fireproofing  and  weighting  silk  by  a  uniform  impregnation  with 
the  hydrogel  of  zirconium  hydroxide.  The  material  is  steeped 
in  a  solution  of  a  zirconium  salt,  e.g.,  zirconium  acetonitrate 
(obtained  by  evaporating  a  solution  of  zirconium  nitrate  and 
acetic  acid).  A  neutral  salt  is  added  (as  MgSOJ,  the  product 
drained  and  heated  for  45  minutes  at  60°-70°.  For  fireproofing, 
the  impregnated  material  is  treated  with  dilute  phosphoric  acid, 
or  precipitated  zirconium  phosphate  is  dissolved  in  a  concen- 
trated solution  of  oxalic  acid  and  the  material  impregnated,  with 
or  without  subsequent  treatment  with  a  neutral  salt,  and  heated 
at  70°. 

1921.  Rietz  (592).    U.  S.  Patent  1,366,101.    C.  A.  15,  934. 
Clouding  glass,  enamels,   and  glazes.    Fluorides   are  used  in 

conjunction  with  compounds  of  Zr.  As  example  a  frit  consisted 
of  Na2C03,  feldspar,  quartz,  native  Zr02,  and  sodium  silico- 
fluoride.  The  fluorides  are  used  in  larger  proportions  than 
hitherto.  The  batches  must  contain  a  large  proportion  of  Si02. 
1919.  Rosenhain  and  Rodd  (606).  U.  S.  Patent  1,307,881.  C.  A. 

18,  2261. 
Production  of  a  basic  zirconium  sulphate.    This  is  prepared 


PATENTS  145 

by  adding  an  alkali,  as  NH4OH  to  a  solution  containing  zirconium 
sulphate  and  hydrochloric  acid  until  so  far  neutralized  that  a 
permanent  precipitate  begins  to  form  and  then  allowing  the  pre- 
cipitation to  proceed  without  further  addition  of  alkali. 
1919.     Rosenhain  and  Rodd   (607).    U.  S.  Patent  1,307,882.    C.  A. 

13,  2261. 

Production  of  a  basic  zirconium  chloride.  This  compound  has 
the  composition  Zr508Cl4.22H20  and  is  soluble  in  water.  Dis- 
solve wet  Zr(OH)4  in  equal  volumes  of  HC1  and  H20  (D.  1.15) ; 
concentrate  the  solution  until  crystals  form  on  cooling.  These 
are  mixtures  of  the  above  with  ZrOCl2 .  8H20.  On  recrystallizing 
from  HC1  (D.  1.08)  the  basic  chloride  crystallizes  alone. 
1919.  Rosenhain  and  Rodd  (608).  U.  S.  Patent  1,307,883.  C.  A. 

13,  2261. 

Production  of  a  basic  zirconium  sulphate.  This  salt  has  the 
composition  5Zr02 .  2S03 . 14H20  and  is  sparingly  soluble  in  water. 
It  is  formed  from  the  basic  chloride,  Zr508Cl4.22H20,  by  dis- 
solving in  thirty  times  its  weight  of  water  and  adding  H2S04  ac- 
cording to  the  equation 

Zr508Cl4  +  2H2S04  =  5Zr02.2S03  +  4HC1. 

1904.  Ruff  (622).     Ger.  Patent  286,054.     C.  A.  10,  956. 
Preparation  of  zirconium  carbide.     The  oxide  is  mixed  with 

coal  or  placed  in  a  carbonizing  atmosphere  and  heated.  For 
example,  1  k.  crude  or  purified  Zr02  is  mixed  with  300  g.  coal 
and  heated  in  a  graphite  crucible.  At  about  1900°  a  copious 
evolution  of  gas  sets  in  and  continues  on  increase  of  temperature. 
It  is  raised  to  2100°.  There  is  direct  production  of  a  fine  pow- 
der. The  fineness  is  determined  by  the  height  of  the  final  tem- 
perature. 

1905.  Sander    (632).     Ger.  Patents   133,701,   137,568,   and   137,569. 

C.  B.  1905,  I,  1290. 

Zirconium  incandescent  electric  lamps.  The  filaments  are 
made  of  zirconium  hydride  and  nitride  or  of  zirconium  carbide 
(90  parts)  and  rhodium  (or  the  corresponding  amount  of  oxide) 
(10  parts),  which  are  worked  into  form  by  suitable  methods. 
These  filaments  are  very  hard,  not  brittle,  and  have  a  metallic 
appearance.  They  conduct  electricity  as  the  metal  does.  The 
lamps  are  evacuated  or  filled  with  hydrogen.  The  normal  effi- 
ciency in  use  is  2  watts  per  candle  power.  They  burn  700-100Q 
hours  and  give  only  a  slight  deposit  in  the  lamps. 


146  ZIRCONIUM  AND  ITS  COMPOUNDS 

1906.    Sander   (633).     Ger.  Patents  147,316  and  154,691. 

These  refer  to  the  production  of  zirconium  from  the  hydride 
and  nitride. 
1920.    Sicard  (656).    U.  S.  Patent  1,335,991.    C.  A.  14,  1519. 

Alloy  of  iron,  zirconium,  and  titanium.  This  is  formed  by 
mixing  baddeleyite,  rutile,  and  scrap  iron  with  carbon  in  sufficient 
quantity  not  only  to  reduce  the  oxides  but  to  combine  the  metals 
to  form  a  complex  carbide  which  is  smelted  in  an  electric  furnace. 
The  alloy  may  contain  Zr  35-40  p.c.,  Ti  4-5  p.c.,  C  4-8  p.c.,  and 
Fe  57-47  p.c.,  which  may  be  used  in  forming  zirconium  steel. 
1920.  Sicard  (657).  U.  S.  Patent  1,335,992.  C.  A.  14,  1519. 

Zirconium  steel.  This  ferro-alloy  is  formed  by  adding  the 
alloy  of  Fe,  Zr,  Ti,  and  C  to  molten  steel.  The  Ti  prevents  oxi- 
dation of  the  Zr. 

1913.  Stern  (678).     Ger.  Patent  261,142.     C.  B.  1913,  II,  187. 

Use  for  weighting  silk.  The  fibers  are  impregnated  with  solu- 
tions of  tungsten  and  molybdenum  salts  and  then  treated  with  a 
solution  of  a  zirconium  salt.  Precipitate  forms  on  the  fiber.  The 
baths  may  be  reversed. 

1914.  Stern  (679).     Ger.  Patent  276,423.     Z.  angewand.  Chem.  27, 

500. 

This  refers  to  the  use  of  zirconia  in  gas  mantles. 
1919.    Wade  (755).    Brit.  Patent  153,113.    C.  A.  15,  930. 

A  new  basic  sulphate  of  zirconium  of  the  composition 
5Zr02.3S03.13H20,  free  from  Fe,  Ti,  and  Si,  is  obtained  by  add- 
ing H2S04  in  the  requisite  quantity  to  a  solution  of  zirconyl 
chloride  containing  free  acid,  preferably  HC1.  The  basic  zirconyl 
sulphate  is  precipitated  on  heating. 
1910.  Weintraub  (796) .  Brit.  Patent  25,033.  C.  A.  6,  1406. 

Preparation  of  pure  zirconium.    The  metal  may  be  prepared 
by  the  action  of  hydrogen  upon  zirconium  halides  at  the  tem- 
perature of  the  electric  arc. 
1919.    Weintraub  (797).    U.  S.  Patent  1,306,568.     C.  A.  13,  2113. 

Preparation  of  pure  zirconium.  Halogen  compounds  of  zir- 
conium, as  the  chloride,  are  reduced  by  the  action  of  hydrogen 
mixed  with  the  vapor  of  sodium  or  potassium  in  a  reaction  vessel 
heated  externally  by  a  gas  burner  and  internally  by  an  incan- 
descent filament.  The  temperature  is  high  enough  to  volatilize 
the  NaCl  formed  but  not  to  volatilize  the  metal — about  1600° 
abs.  The  gas  stream  may  be  omitted  and  the  reduction  take 


PATENTS  147 

place  in  a  vacuum.    The  metal  prepared  in  this  way  contains 
only  0.001  p.c.  of  impurities. 

1910.    Weiss   (798).    Ger.  Patent  230,757.     C.  B.  1911,  320,  or  II, 

524   (?). 

This  refers  to  the  use  of  zirconia  as  an  abrasive  and  polishing 
agent. 

1910.  Weiss  (799).  Ger.  Patent  235,495.  Chem.  Ztg.  Rep.  35,  320. 
The  preparation  of  white  pigment  and  lacs.  Starting  with 
most  of  the  compounds  of  zirconium  (oxide,  silicate,  carbonate, 
phosphate,  sulphite)  a  pure  white  pigment  may  be  obtained  on 
ignition.  This  is  stable  at  high  temperatures  and  most  resistant 
to  chemical  action.  It  is  not  attacked  by  acid  or  alkali  and 
not  changed  by  hydrogen  sulphide.  It  is  not  poisonous.  It  is 
worked  up  with  the  usual  vehicles. 

1910.  Weiss  (800).    U.  S.  Patent  982,326.     Chem.  Ztg.  Rep.  36,  320. 
Production  of  ferro-zirconium. 

1911.  Weiss  (803).     Ger.  Patent  237,624.     Chem.  Ztg.  Rep.  35,  1262. 
This  refers  to  the  use   of  zirconia   as   an   inert  powder   for 

medicinal  purposes. 
1885.    Welsbach  (810).     Ger.  Patent  39,162.     Ber.  d.  chem.  Ges.  20, 

Ref.  406. 

The  use  of  zirconia  in  gas  mantles.     This  use  is  along  with 
oxides  of  the  rare  earths,  giving  a  white  light.    The  making  of 
the  mantles  is  described. 
1889.    Welsbach  (811).    U.  S.  Patent  409,653.     Chem.  Ztg.  13  (2), 

1192. 

The  preparation  of  zirconium  nitrate.  Zircon  is  pulverized, 
washed,  digested  with  concentrated  HC1  to  remove  iron,  mixed 
with  twice  its  weight  of  Na2C03,  and  heated  to  a  white  heat.  The 
melt  is  leached  with  water  and  the  insoluble  residue  treated  with 
excess  of  H2S04,  which  excess  is  later  driven  off.  The  zirconium 
sulphate  is  dissolved  in  water,  precipitated  by  NH4OH,  and  the 
zirconium  hydroxide  dissolved  in  nitric  acid.  This  nitrate  may 
be  used  in  gas  mantles. 
1905.  Wolfram  Lampen  Ges.  (822).  Ger.  Patent  200,300.  C.  A. 

2,  2909. 

A  means  of  overcoming  the  brittleness  of  tungsten  filaments. 
Zirconium  is  added  to  tungsten  and  the  filaments  are  formed  with 
the  addition  of  tin  chloride-cellulose  or  glacial  acetic  collodion, 


148  ZIRCONIUM  AND  ITS  COMPOUNDS 

denitrated,  sintered,  decarbonized  by  heating  in  hydrogen,  and 
heated  to  incandescence  by  electric  current. 
1907.    Zerning    (830).    Brit.   Patent  20,233.    Soc.   Chem.   Ind.   27, 

1197. 

Lamp  filaments.  Heat  zirconia  with  zinc  dust  in  a  hydrogen 
atmosphere.  Then  treat  with  acid  to  remove  the  zinc  oxide  and 
wash  with  water,  alcohol,  and  ether,  successively.  The  zirconium 
retains  or  combines  with  the  hydrogen.  Mix  this  product  with 
12-16  p.c.  of  a  suitable  binder,  as  nitro-cellulose  in  anyl  acetate 
to  which  some  castor  oil  has  been  added,  and  use  to  coat  the 
inside  of  iron  vessels  in  which  lamp  filaments  are  heated. 


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1428. 

716.  1871,    Troost    and    Hautefeuille,      737. 

Zirconyl     chloride.        Compt. 
rend.  73,  570. 

717.  1871,    Troost    and    Hautefeuille       738. 

Spectrum.     Compt.    rend.    73, 
620. 

718.  1872,    Troost    and    Hautefeuille, 

Action   of  silicon   chloride   on      739. 
zirconia.      Compt.     rend.     75, 
1821. 

719.  1886,  Troost  and  Ouvrard,  Potas-      740. 

sium-zirconium  phosphate. 
Compt.  rend.  102,  1422. 

720.  1887,  Troost  and  Ouvrard,  Sodi-      741. 

um  -  zirconium    phosphate. 
Compt.  rend.  105,  30. 

721.  1887,  Troost  and  Ouvrard,  Zircon      742. 

not  isomorphous  with  thorium 
silicate.  Compt.  rend.  105,  258. 

722.  1898,  Truchot,  Occurrence  of  zir-      743. 

con.   Chem.  News  77,  134,  145. 

723.  1902,  Tucker  and  Moody,  Boride. 

J.  Chem.  Soc.  81,  14.  744. 

724.  1898,  Turner,  Zircon  in  California 

gold  sands.    Amer.  J.  Sci.  (4) 

5,  426.  745. 

725.  1916,  Production  in  the    United 

States.  U.  S.  Geol.  Surv.  Min- 
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726.  1797,  Vauquelin,  Analysis  of  hya-      746. 

cinth:    Properties   of   zirconia. 
Ann.  chim.  phys.  22,  179. 

727.  1916,  Vegard,  Results  of  crystal 

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3021. 

728.  1916,  Vegard,  Crystal  structure  of 

zircon.   Phil.  Mag.  (6)  82,  65. 

729.  1916,    Vegard,    Crystal    structure      748. 

and  space  lattice.    Phil.  Mag. 
(6)  82,  505. 

730.  1917,    Vegard,    Crystal    structure      749. 

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731.  1918,    Vehle,    Arc    spectrum.    Z. 

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1419. 

732.  1891,  V  enable,  Occurrence  of  zir- 

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Soc.  8,  74.  751. 

733.  1891,    Venable,    Preparation     of 

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734.  1894,  Venable,  Chlorides:  Separa-      752. 

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Am.  Chem.  Soc.  16,  469. 

735.  1895,  Venable,  Chlorides.   /.  Am.      753. 

Chem.  Soc.  17,  842. 

736.  1898,      Venable,      Revision      of 


atomic  weight.   J.  Am.  Chem. 
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1918,  Venable,  Luminescence   of 
zircons.  J.  Elisha  Mitchell  Sci. 
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1919,  Venable,   Technical    appli- 
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compounds.  J.  Elisha  Mitchell 
Sci.  Soc.  34,  157. 

1921,  Venable,  Chemical  behav- 
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Mitchell  Sci.  Soc.  36,  115. 

1895,  Venable    and    Baskerville, 
Sulfites.  J.  Am.  Chem.  Soc.  17, 
448. 

1897,  Venable    and    Baskerville, 
Oxalates.    J.  Am.  Chem.  Soc. 
19,  12. 

1898,  Venable    and    Baskerville, 
Zirconyl  halides.  /.  Am.  Chem. 
Soc.  20,  231. 

1898,  Venable  and  Belden,  Prop- 
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Chem.  Soc.  20,  273. 

1917,  Venable  and  Bell,  Revision 
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Chem.  Soc.  39,  1598. 

1921,  Venable  and  Dietz,  Reac- 
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methane.  J.  Elisha  Mitchell 
Sci.  Soc.  38. 

1918,  Venable     and     Blaylock, 
Basic   zirconyl    benzoates   and 
salicylates.  /.  Am.  Chem.  Soc. 
40,  1746. 

1896,  Venable  and  Clarke,  Alka- 
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434. 

1918,  Venable   and   Giles,   Basic 
zirconyl     chromate.      J.    Am. 
Chem.  Soc.  40,  1653. 

1920,  Venable  and  Jackson,  Ac- 
tion of  carbon  monoxide  and 
chlorine  on  zirconia.  J.  Elisha 
Mitchell  Sci.  Soc.  36,  87. 

1920,  Venable  and  Jackson,  Hy- 
drolysis of  compounds  at  low 
temperatures.  J.  Am.  Chem. 
Soc.  42,  2531. 

1919,  Venable  and  Smithey,  Cer- 
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Chem.  Soc.  41,  1722. 

1877,  Vincent,  Conduct  with  tri- 

methylamine.  Bull.  Soc.  chim. 

27,  194. 
1880,  Vincent,  Conduct  with  di- 

methylamine.  Bull.  Soc.  chim. 

S3,  156. 


168 


ZIRCONIUM  AND  ITS  COMPOUNDS 


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755.  1919,     Wade,     Zirconium     salts. 

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756.  1913,  Wagner,  Hydrolysis  of  zir- 

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757.  1898,  Walker>  Separation  by  hy- 

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Eng.  Min.  J.  51,  520.  777. 

759.  1913,  Walter,  Valve  action  of  zir- 

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760.  1857,    Warren,    Zirconium-potas- 

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764.  1920,   Washington,   Zirconium   in 

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765.  1911,  Watson  and  Hess,  Zirconif-      784. 

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766.  1912,   Watson   and   Hess,   Occur- 

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767.  1915,      Watson,      Zircon-bearing 

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768.  1863,    Weber,    Analysis    of    fer-      788. 

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770.  1868,     Websky,     Occurrence     in 

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771.  1905,   Wedding,   Zirconium   lamp 

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85. 


1902,  Wedekind,    Reduction    of 
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1903,  Wedekind,  Colloidal  zirco- 
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1903,  Wedekind,   Preparation    of 
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1904,  Wedekind,   Preparation    of 
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331. 

1905,  Wedekind,    Reduction    by 
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1906,  Wedekind,  Native  zirconia 
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1907,  Wedekind,    Carbide    from 
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Chem.  Ztg.  31,  654. 

1908,  Wedekind,  Colloidal  zirco- 
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289. 

1908,  Wedekind,  Iron-free  zir- 
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1910,  Wedekind,  Colloidal  zirco- 
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1910,  Wedekind,  Native  zirconia. 
Ber.  43,  290. 

1911,  Wedekind,  Conduct  of  zir- 
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Ber.  44,  1753. 

1912,  Wedekind,    Metallic    zirco- 
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1908,  Wedekind  and  Lewis,  Spe- 
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1909,  Wedddnol      and      Lewis, 
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1909,  Wedekind  and  Lewis,  Ana- 
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456. 

1910,  Wedekind    and    Lewis,    A 
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1912,  Wedekind    and    Lewis,    A 
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1913,  Wedekind     and     Pintsch, 
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1914,'  Wedekind  and  Rheinboldt, 
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SUBJECT  INDEX 


Acetates,  110,  111. 

basic  zirconyl  acetates,  111. 

normal  acetate  hydrolysis,  111. 

normal   zirconium   acetate,   111. 

zirconyl  acetate,  111. 
Acetylacetonate,  115. 
Adelfolith,  20. 
Adsorption  compounds,   32. 
Alvite,   20,   21. 
Amide,  46,  47. 
Analytical  methods,  120,  125. 

qualitative,    120,    121. 

quantitative,   121,  122. 

separations,   123,   124,  125. 
Anderbergite,  20,  21. 
Antimonate,  pyroantimonate,  93,  94. 
Applications,  technical,  125-132. 

abrasives,    132. 

alloys,    128-129. 

chlorinating  agent,    132. 

clouding  agent,  130. 

colloidal  uses,  131. 

combustion  tubes,  130. 

crucibles,   130. 

electrodes,    129. 

enamels,    130. 

filaments,   127. 

furnace  lining,  129,  130. 

gas   mantles,    127. 

glass,   131. 

insulating  materials,  129. 

jewels,  126. 

medicinal,  131. 

mordanting,   131. 

oxy-hydrogen  light,  126,  127. 

pigment,    131. 

reducing  agent,  128. 

refractories,  130. 

scavenger,    129. 

weighting  filter,  131. 
Arrhenite,  20,  21. 
Arsenates,  93. 
Astrophyllite,  20,  21. 
Auerbachite,   20,   21. 
Azide,  46. 

Baddeleyite,  20,  98. 

Beccarite,   20,    21. 

Benzoate,  basic  zirconyl  benzoates,  114. 


Bibliography,   149-169. 
Boride,   49,   50. 


Brazilite,  20,  21. 

Bromides,  addition  compounds,  72. 

basic  zirconyl  bromides,  73. 

normal  zirconium   tetrabromide,  72. 

preparation    of,    72. 

properties  of,  72. 

zirconyl    bromide,   72. 

Carbide,   zirconium   carbide,  30,   47. 
Carbonates,   absorption  of  carbon  dioxide 
by   hydroxide,    110. 

basic  zirconyl  carbonates,  110. 

precipitation     by    alkaline     carbonates, 


Catapleiite,  20,  21,  103. 

Chalkolamprite,  20,  21. 

Chlorate,     basic     zirconyl     chlorate,     71 ; 

normal   zirconium   chlorate,   71. 
Chromate,  basic  zirconyl  chromate,  94. 
Citrate,     ammonium     zirconium     citrate. 

Ill,  112. 

Cyanides,  zirconyl  cyanides,  116. 
Cyrtolite,  20,  21. 

Discovery  of  the  element,   15. 
Distribution  of  ores  and  minerals,  17,  18. 

Elpidite,  20,  21,  103. 
Erdmannite,  20,  21. 
Eudialyte,  20,  21. 
Euxenerde,  20,  21. 

Fergusonite,  20,   21. 

Ferricyanide,   zirconyl  ferricyanide,  116. 
Ferrocyanide,  zirconyl  ferrocyanide,  116. 
Fluorides,   normal  zirconium   fluoride,  53. 
preparation  of,  53. 
properties  of,  54. 

constitution  of  hydrate,  54. 

double  salts  (vid.  fluozirconates),  55. 

loss  in  analysis,  54. 

zirconyl  fluoride,  54. 
Fluozirconates,   55. 

ammonium  fluozirconate,  56,  57. 

barium  fluozirconate,  61. 

cadmium  fluozirconate,  61. 

caesium  fluozirconate,  58,  59. 

calcium  fluozirconate,  60. 

copper  fluozirconate,   60. 

lead  fluozirconate,  61. 

lithium  fluozirconate,  55,  56. 

magnesium   fluozirconate,  62. 

manganese  fluozirconate,  62. 

nickel  fluozirconate,  62. 

nickel  and  potassium  fluozirconate,  62. 

potassium  fluozirconate,  57,  58. 

rubidium  fluozirconate,  58. 

silicon   (zirconium  sili co-fluoride ),  63. 

sodium  fluozirconate,  56. 

strontium   fluozirconate,   60. 

thallium  fluozirconate,  63. 

zinc  fluozirconate,  61. 
Formates,  normal  zirconium  formate,  110. 

zirconyl   formate,   110. 
Formulas  for  basic  zirconyl  salts,  33. 

Hiortdahlite,  20,  21. 

History  of  the  element,  15,  16. 

Hyacinth,  17,  18. 

Hydride,  zirconium  hydride,  34,  35. 

Hypophosphite,  92. 

Jacinth,  17. 
Jacupirangite,  20. 
Jargon,  17. 
Jargonium,  16. 

Kochelite,  20,  21. 
Lovenite,   21,   103. 


171 


172 


SUBJECT  INDEX 


Malacone,  20,  21. 
Mengite,   97. 
Mqlybdates,    95,    96. 
Monoxide,  35. 
Mosandrite,  21. 

Nitrates,    addition    compounds    with    zir- 

conyl  nitrate,  89. 
basic  zirconyl  nitrates,  88. 
dialysis  of  basic  nitrates,  89. 
existence   of  normal  zirconium   nitrate, 

87. 

hydrates  of  zirconyl  nitrate,  87. 
hydrolysis  of  zirconyl  nitrate,  88,   89. 

zirconyl  nitrate,  87. 
Nitrides,  30,  45,  46,  47. 
Noria,  16. 

Occurrence  of  zirconium   compounds,   16- 

21. 

Olivieraite,   21. 
Ores,  distribution  of,  17,  18. 
Organic  acids,   110-113. 
Organic  bases  and  tetrahalides,  114-119. 

addition  compounds  formed,  117-118. 

precipitates  formed,  119. 
Oxalates,    ammonium    zirconium    oxalate, 
112,  113. 

basic  zirconyl  oxalates,  112. 

solubility   of  hydroxide  in   oxalic   acid, 
112. 

zirconyl  oxalate,  112. 
Oxide  (vid  zirconia). 
Oxysulphide,  49. 

Patents,  133-148. 

abrasive,   143. 

abrasive  and  polishing  agent,  147. 

alloy  for  high  melting  point  and 
ductility,  139. 

alloy  Zr,  Fe,  Si,  Cr,  Ni,  Mn,  135. 

alloy  Zr,   Fe,  Ti,   146. 

alloy  Zr,  Nb,  Ta,  137. 

alloy  Zr,  Ni,  134. 

alloy  Zr,  Ni,  Al,  Si,  135. 

alloy  Zr,  Ni,  Al,   Si,  W,  Fe,   135. 

alloy  Zr,  Ni  or  Co,  Cr,  135. 

alloy  Zr,  Pb,  143. 

alloy  Zr,  Sb,  141. 

alloys  for  filaments,  electrodes,  etc., 
144. 

alumino-thermic  reduction,  134. 

basic  zirconyl  chloride,  145. 

basic  zirconyl  sulphate,   144,  145,   146. 

basic  zirconyl  sulphate  and  chloride, 
137. 

brittleness  of  tungsten  filaments  re- 
moved by  Zr,  147. 

carbide  preparation,  145. 

castings,   142. 

chemical  application  of  zirconia,  138. 

clouding  agent  for  enamels,  142. 

clouding  agent,  142. 

clouding  glass,  enamels,  and  glazes,  144. 

clouding  composition  for  enamels,  136. 

colloid,  use  of,  141. 

colloidal  zirconium,  140. 

crystallizing  zircon,  138. 

cyanonitride,   133. 

drawing   filaments,   139. 

enamels,   136. 

enamels,  white,  142. 

ferro  alloys  containing  carbide,  144. 

ferro-zirconium,  134,  147. 

ferro-zirconium  alloys,  137. 

ferro-zirconium   (steel),  146. 

filament,  improvements  detailed,  138. 

filament,  improvements  in  production, 
138. 


Patents — Continued. 

filament  for  lamps,  136,  145,  148. 

filament   production,   136. 

filament  solder,  141. 

fire-proofing  and  weighting  silk,  144. 

fusion  of  zirconia  with  caustic  alkalis, 

134. 

gas   mantles,    146,    147. 
inert  powder  for  medicinal  use,  147. 
iron  free  zirconia  for  enamels,   138. 
iron  free  zirconia,  detailed,   138. 
manufacture    of    alloys    for    filaments, 

140. 

metallic   zirconium    or    its    alloys,    pro- 
duction, 136. 
nitrate  preparation,  147. 
nitride  production,  133. 
nitride  purification,  134. 
opacifier  for  enamels,  138. 
ores  in  gold   extraction,   139. 
peptizing    coagulated    zironium    colloid, 

140. 
porcelain   (clay,  feldspar  and  zirconia), 

135. 
recovery    of    valuable    constituents    in 

zirconium  ores.  143. 
refractory  of  zirconia  and  alumina,  139. 
refractory    of    zirconia    and    chromite, 

139 

refractory  vessels,  139,  140. 
separation  from   iron,   133. 
separation  as  pyrophosphate,  134. 
separation    from    rare    earths    by    elec- 
trolysis, 135. 
silicide,    oxide    and    salts,    preparation, 

139. 

utensils  of  zirconia,  133. 
weighting  silk,  142,  146. 
white  pigment  and  lacs,  147. 
zirconia  ores,   purification,   143. 
zirconia,  preparation  from  ore,  137. 
zirconia,  pure,  from  zirkite,  138. 
zirconia  purifying,   142. 
'     zirconium,  pure,  production,  141,  146. 
zirconium,  preparation,  143. 
zirconium  preparation  from  hydride  or 

nitride,  146. 
Pentoxide,  44. 
Perchlorates,     acid     zirconyl    perchlorate, 

71. 

basic  zirconyl  perchlorate,  71. 
Periodate,  basic  zirconyl  periodate,  75. 
Perzirconates,  lithium   perzirconate,  107. 
potassium  perzirconate,  107. 
sodium   perzirconate,   107. 
Phosphates,  basic  zirconyl  phosphates,  91. 

double  salts  with  alkalis,  92. 

double  salts  with  sodium,  92,  93. 
hypophosphite,  92. 
pyrophosphate,   90. 
solubility    of    hydroxide    in    phosphoric 

acid,  89. 

'  subphosphate,  91. 
Phosphide,   51,    52. 
Polymignite,   21,    97. 
Pyrochlor,  21. 
Pyrophosphate,    zirconium   pyrophosphate, 

92. 
Pyroracemate  (propanonate),  115. 

Rosenbuschite,   23. 

Salicylates,  basic  zirconyl  salicylates,  115. 
Selenates,  basic  zirconyl  selenates,  86. 
Selenite,  basic  zirconyl  selenites,  85,   86. 

normal  zirconium  sele.nite,  85. 
Silicates,   artificial,   103. 

calcium  zirconium  silicate,  104. 


SUBJECT  INDEX 


173 


Silicates — Con  tinued. 

lead-zirconium    silicate,    104. 

potassium-zirconium   silicate,  104. 

sodium-zirconium   silicate,   103,   104. 

vid  zircon. 
Silicide,  50,  51. 
Silico-fluoride,  63. 
Subphosphate,  91. 
Sulpharsenate,  93. 
Sulphates,  acid  zirconium  sulphate,  78. 

acid  zirconyl  sulphate,   81. 

basic  zirconyl  sulphate,  80,  81,  82. 

double   salts    with    zirconium    sulphate, 
80. 

double  salts  with  zirconyl  sulphate,  83. 

hydrolysis   of  zirconium    sulphate,   78. 

normal  zirconium  sulphate,  77. 

preparation  of  zirconium  sulphate,  77. 

properties  of  zirconium  sulphate,  77. 

zirconyl  sulphate,  81. 
Sulphite,  basic  zirconyl  sulphite,  76. 

normal   zirconium   sulphite,   76. 

Tachyaphaltite,  21. 
Tantalite,  21. 

Tartrates,  basic  zirconyl  tartrate,  113. 
zirconyl-ammonium   tartrate,   113. 
zirconyl-potassium  tartrate,   113. 
solubility    of    hydroxide    in    ammonium 

tartrate,    113. 
solubility  of  hydroxide  in  tartaric  acid, 

113. 

Tellurate,   zirconyl  tellurate,  86. 
Tellurite,    zirconyl   tellurite,   86. 
Thiocyanate,   zirconium   thiocyanate,   116. 
organic    double     compounds    with     zir- 
conium thiocyanate,  116. 
Titanates,  natural  occurring  titanates,  97. 

zirconvl  titanates,  97. 
Trioxide^  44,   45. 

Tungstates,      ammonium     zirconyl     tung- 
states,   95. 

basic  zirconyl  tungstates,  94. 
potassium  zirconyl  tungstates,   95. 

Uhligite,  21. 

Valerianate,   115. 
Vanadate  compound,  96. 

Wohlerfte,  21,  103. 

Zircon,  altered,  98. 
analyses,   98. 
artificial,   102. 
chemical  behavior,  99. 
color,  19. 

composition,   17.    18,   98. 
crystal  form,  97. 
luminescence,   99-102. 
melting    point,    99. 
minerals,  20. 


Zircon — Continued. 

occurrence,  17,  18. 

specific  gravity,  99. 

types,  21. 
Zirconates,   33. 

barium  zirconate,  108,  109. 

calcium  zirconate,   108. 

formation  of  zirconates,  104. 

lithium  zirconate,  107. 

magnesium   zirconate,   108. 

perzirconates,   107. 

potassium  zirconate,   107. 

sodium  zirconate,   106. 

strontium  zirconate,  108. 
Zirconia,  boiling  point,  39. 

chemical  conduct,  39,  40. 

coefficient  of  expansion,  39. 

conductivity  for  electricity,  39. 

conductivity  for  heat,  39. 

crystalline  form,  39. 

crystallization,  38. 

heat  of  formation,  39. 

light    emission,    39. 

melting   point,    39. 

native,  36. 

occurrence,  36. 

preparation  from  zircons,  37,  38. 

porosity,   39. 

purification  of  native,  36,  37. 

reflecting  power,  39. 

specific  gravity,   39. 

specific  heat,  39. 

volatilization,    39. 
Zirconium,   adsorption   compounds,   32. 

aluminum  compounds,  23. 

amorphous,  23,  26. 

atomic  number,  31. 

atomic  weight,  31. 

cations,  32. 

chemical   behavior,  30. 

colloidal  metal,  26. 

electrical  properties,  28. 

hydroxide,   40. 

hydroxide  dehydration,  40,  41. 

hydroxide   solubility,   41,   42. 

melting  point,   27. 

monoxide,  35. 

normal  salts,  32. 

optical   properties,   28. 

oxide — vid,    zirconia. 

pentoxide,  44. 

preparation,   22,   23,  24. 

specific  gravity,  27,  28. 

spectrum,  28,  29. 

trioxide,   44,   45. 

values,  32,  33. 
Zirconsulphuric  acid,  79. 
Zirconyl  radical,  32,  33. 
dehydration,  41. 
formation,   43. 

ionic  migration,  105. 
solubility,   41,   42. 

zirconyl  hydroxide,   40,   41,  105. 
Zirkelite,   19,  20,  21,  99. 


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